Anatomy Study Guide

The University of Iowa

Center for Credit Programs

Distance Education Study Guide

for

027:053 Human Anatomy

College of Liberal Arts and Sciences Integrative Physiology

Course Prepared by

Kenneth E. Mobily, Ph.D.

3 Semester Hours 8 Written Assignments

4 Examinations


Copyright © 2007 The University of Iowa. All rights reserved.

No part of this publication may be reproduced in any form by any means

without permission in writing from the publisher.

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reasonable accommodations in order to participate in this program, please contact the Center for Credit Programs to discuss your needs.

Distance Education Division of Continuing Education

250 Continuing Education Facility Iowa City, IA 52242-0907

Telephone: 319.335.2575 • Toll free: 800.272.6430

Fax: 319.335.2740 • E-mail: [email protected] Web: http://continuetolearn.uiowa.edu/ccp/

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http://continuetolearn.uiowa.edu/ccp/

mailto:[email protected]

Distance Education The University of Iowa

027:053 Human Anatomy College of Liberal Arts and Sciences

Integrative Physiology

Course Contents

Course Lessons

About the Coursewriter and Instructor ................................................................... 5!Introduction: About This Course ............................................................................. 6!

Overview ........................................................................................................ 6!Course Goals .................................................................................................. 6!Required Course Materials ........................................................................... 7!How To Study ................................................................................................ 7!Web and E-mail ............................................................................................. 9!Examinations ............................................................................................... 11!Evaluation and Course Grade ...................................................................... 11!

UNIT 1 INTRODUCTION ..................................................................................... 13!Lesson 1 Orientation ............................................................................................. 14!Lesson 2 Embryology ............................................................................................ 18!UNIT 2 BASIC ORGANIZATION.......................................................................... 24!Lesson 3 Cells ........................................................................................................ 25!Lesson 4 Tissues .................................................................................................... 31!

Written Assignment #1 ............................................................................... 38!Lesson 5 Integumentary System ........................................................................... 40!Lesson 6 Bone and Skeletal Tissue ....................................................................... 45!

Written Assignment #2 ................................................................................ 51!Examination #1 ............................................................................................ 51!

UNIT 3 MOVEMENT ............................................................................................ 52!Lesson 7 The Axial Skeleton .................................................................................. 53!Lesson 8 The Appendicular Skeleton .................................................................... 59!Lesson 9 Joints ...................................................................................................... 66!

Written Assignment #3 ............................................................................... 70!Lesson 10 Muscle Tissue ........................................................................................ 71!Lesson 11 Muscle System ...................................................................................... 77!

Written Assignment #4 ............................................................................... 83!Examination #2 ........................................................................................... 83!

UNIT 4 INTEGRATION ........................................................................................ 85!Lesson 12 Nervous Tissue ..................................................................................... 86!Lesson 13 Central Nervous System ....................................................................... 94!Lesson 14 Peripheral Nervous System ................................................................ 108!

Written Assignment #5 .............................................................................. 114!Lesson 15 Autonomic Nervous System ................................................................ 116!

Written Assignment #6 .............................................................................. 121!Lesson 16 Special Senses ...................................................................................... 122!

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Lesson 17 Endocrine System ............................................................................... 129!Examination #3 .......................................................................................... 135!

UNIT 5 VISCERAL SYSTEMS............................................................................. 136!Lesson 18 Heart .................................................................................................... 137!Lesson 19 Blood Vessels and Lymphatics ........................................................... 144!

Written Assignment #7 .............................................................................. 154!Lesson 20 Respiratory System ............................................................................. 155!Lesson 21 Digestive System ................................................................................. 162!

Written Assignment #8 ............................................................................. 169!Lesson 22 Urinary System .................................................................................. 170!Lesson 23 Reproductive System .......................................................................... 175!

Examination #4 (FINAL) ............................................................................ 180!Course Evaluation ...................................................................................... 181!Transcript ................................................................................................... 181!

Distance Education Policies and Instructions

Be sure to read the Distance Education (DE) Policies and Procedure before beginning this course. It is available on the ICON course site under Content; students who order the optional print material will receive a print copy by mail.

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About the Coursewriter and Instructor

KENNETH E. MOBILY received his

bachelor's and master's degrees in therapeutic

recreation and was clinical supervisor of

therapeutic recreation in Cincinnati, Ohio, for

three years. He completed his Ph.D. in 1981 from

the University of Iowa in physical education. He is

a Professor at The University of Iowa where he

teaches a variety of professional courses in

therapeutic recreation. He also teaches Human Anatomy for the

Department of Integrative Physiology at Iowa. His primary research area

is exer

obily may be contacted by e-mail at: ken-

cise and aging.

Professor M

[email protected] .

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Introduction: About This Course

Overview

This course is designed to give you a basic understanding of human

anatomy, with particular emphasis on organelles, tissues, organs, and

systems. You will finish this course with a background knowledge of the

structure of the human body. You may want to capitalize on your

introductory knowledge through further study.

In preparing this study guide, I have focused on structure and the

relations between structures. While this may be rather obvious because the

preceding sentence essentially embodies the definition of anatomy, it is

easier said than done.

At the same time, you should be aware that function and structure

are related. How an anatomical component works is almost always related

to its cellular or gross structure. Red blood cells are bi-concave in shape

(structure) and this allows for more surface area for the cell to bind and

transport oxygen or carbon dioxide (function). We have a generous range

of motion (function) at the shoulder joint because of the shape (structure)

of the articulating bones—the head of the humerus and the glenoid fossa of

the scapula. Function often follows form.

Course Goals

Accordingly, the general goals of this course are three:

1. To gain a basic understanding of the organs, systems, and tissues

covered,

2. To relate systems and tissue to one another and understand how they

work together,

3. And to understand the role of each organ, system, and tissue.

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Required Course Materials

Materials Provided by the CCP

The following items may be accessed from the ICON course site

(under “Content”). They are also available in print from our office, and

may be purchased for an additional fee.

! Course Study Guide ! Course Syllabus ! Textbook and Materials Order Form ! Distance Education Policies and Instructions

Textbooks/Course Materials to Purchase Independently

! Marieb, Elaine, Jon Mallatt, and Patricia Wilhelm. Human Anatomy, 5th edition. San Francisco, CA: Pearson-Benjamin Cummings, 2008.

The course textbooks may be ordered from a local bookstore (see

Textbook and Materials Order Form) or from the vendor of your choice.

Note: If you purchase items from an alternate bookseller, it is imperative

that you obtain the correct editions.

How To Study

The units of study are organized around general concepts. These

organizing concepts are indicated below by unit numbers, with course

lessons indicated by letters. The chapters in Marieb, Mallatt, and Wilhelm

pertaining to the lessons are indicated to the side of each.

Unit 1: Introduction

A. Orientation (Chapter 1)

B. Embryology (Chapter 3)

Unit 2: Basic Organization

A. Cells (Chapter 2)

B. Tissues (Chapter 4)

C. Integumentary System (Chapter 5)

D. Bone and Skeletal Tissue (Chapter 6)

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Unit 3: Movement

A. Axial Skeleton (Chapter 7)

B. Appendicular Skeleton (Chapter 8)

C. Joints (Chapter 9)

D. Muscle Tissue (Chapter 10)

E. Muscle System (Chapter 11)

Unit 4: Integration

A. Nervous Tissue (Chapter 12)

B. Central Nervous System (Chapter 13)

C. Peripheral Nervous System (Chapter 14)

D. Autonomic Nervous System (Chapter 15)

E. Special Senses (Chapter 16)

F. Endocrine System (Chapter 25)

Unit 5: Visceral Systems

A. Heart (Chapter 18)

B. Blood Vessels (Chapter 19) and Lymphatics (Chapter 20)

C. Respiratory System (Chapter 21)

D. Digestive System (Chapter 22)

E. Urinary System (Chapter 23)

F. Reproductive System (Chapter 24)

At the beginning of each lesson you will be provided with a list of

objectives. You should use the objectives to guide your reading and

studying. You will find that some lessons have few objectives, while others

have a rather lengthy list.

Hence, you are not responsible for material that does not pertain to

the objectives. However, do not allow this to make you casual about your

reading and studying. First of all, successful completion of the written

assignments requires that you know and apply the objectives. The same

is true of the examinations.

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Translated, this means that you are expected to know the material

and objectives very well. This also means that when I tell you to study a

figure or exhibit, I expect that you will study it and not just glance at it.

Anatomy is a very visual science. Lacking actual specimens, the visual

representations of structures become critical. In fact, I would suggest that

you photocopy those illustrations containing a lot of information and clip

off the labels. Then, use the illustration without labels as a self-test at the

end of a unit to determine the extent of your understanding.

Another study hint pertains to pacing. Do not expect to cram for

examinations one or even two days before. You will find that there is a lot

to know. Therefore, learning a little bit every night is a lot easier than

waiting until the "11th hour." Also, review previously covered material

every few days to keep it "fresh" in your mind. Anatomy does require

discipline, but I believe you will find it pays dividends by the end of the

course.

You will also find several sample multiple-choice questions at the

end of each lesson. There are two purposes to the questions. First, they will

help you anticipate the question format you will find on the examinations.

Secondly, the questions will help you home in on objectives you need to

study more. Answers to the questions can be found at the end of each

lesson.

Web and E-mail

This course is delivered on the World Wide Web via ICON (Iowa

Courses Online) http://icon.uiowa.edu/. You can access the course by

logging into ICON with your Hawk ID and password.

Online Tutorials

http://www.uiowa.edu/~online/tutorials/tutorial.html

View the online tutorials, which are provided in Flash format:

topics include instruction on using ICON, WebMail, Hawk ID Tools,

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http://www.uiowa.edu/%7Eonline/tutorials/tutorial.html

http://icon.uiowa.edu/


Security, and more. Please be aware that Distance Education courses do

not use all of the components explained in the ICON tutorial.

Technical Support for Online Students

Technical assistance, including FAQs, software demos and

downloads, and contact information are provided on our technical support

pages: http://continuetolearn.uiowa.edu/ccp/sos/.

Hawk ID Help

http://hawkid.uiowa.edu/

Your Hawk ID and password are sent to you via email or mail the

first time you register at The University of Iowa. If you have forgotten

your Hawk ID password or it has expired (after six months), you may call

the ITS Help Desk at the University and ask them to reset your password.

Please feel free to call our toll-free number (800.272.6430) and select the

phone routing option that connects you with the ITS Help Desk.

E-mail Alias

http://continuetolearn.uiowa.edu/ccp/sos/email.htm

A University of Iowa e-mail alias was created for you when you

enrolled in this course, if you didn't already have one. Your email alias

forwards messages to a specified email address, which can either be a UI

student email account or a non-UI account (e.g. Hotmail, Yahoo…etc.).

Once created, all subsequent e-mail contact from The University of Iowa

will go to your UI email alias. If you have not done so already, you should

login to your student account, i.e. ISIS http://isis.uiowa.edu/, then go to

My Uiowa/My Email and either request a UI email account or provide a

routing address.

E-mail is an official method of communication at The University of

Iowa; you are responsible for all information sent to your e-mail address of

record, and you may carry on official transactions with the University by

sending e-mail from your e-mail address of record. It is important that you

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http://isis.uiowa.edu/

http://continuetolearn.uiowa.edu/ccp/sos/

http://hawkid.uiowa.edu/

http://continuetolearn.uiowa.edu/ccp/sos/email.htm


keep your email routing address in ISIS current if you prefer to use a non-

UI email account.

Examinations

The examinations are forty questions/forty points. The exams stress

application, understanding, and knowing the objectives. Exams are

multiple choice with four foils (choices) for each question. Each exam is

designed to cover about one fourth of the material. However, because

some lessons contain more objectives than others, the number of lessons

covered on each test differs. The exams are NOT comprehensive.

Material Covered on the Exams

Examination #1 Covers lessons 1–6




Please read the information regarding exam scheduling and policies

posted on the ICON course Web site carefully. Students with access to the

Internet must use the ICON course Web site to submit exam requests

online. Students who do not have access to the internet may submit the

Examination Request Form located at the back of this Study Guide (print

version only).

Evaluation and Course Grade

The course consists of eight written assignments and four exams. A

total of 240 points are possible: four exams at 40 points each, (160) and

eight assignments at ten points each (80).

8 Written assignments 80 points (10 percent each) 4 Examinations 160 points Total possible 240 points

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Grading Scale

The grading scale for this class is: 90 percent—A, 80 percent—B, 70

percent—C, 60 percent—D, less than 60 percent—F. Final course grades

will not include plus or minus marks.

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UNIT 1 INTRODUCTION

Lesson 1 Orientation

Lesson 2 Embryology

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Lesson 1 Orientation

Reading Assignment

Read Chapter 1 in the text, focusing on the content that pertains to

the objectives listed below.

Objectives

By the end of this lesson, you should be able to:

1. Define the following levels of structural organization: chemical,

cellular, tissue, organ, system, organism (see Figure 1.1). Give

examples of cells, tissues, organs, and systems.

2. Know anatomical terminology: anatomical position, planes

(saggital, frontal, transverse), body cavities (dorsal, ventral,

thoracic, abdominopelvic, mediastinal, cranial, pleural, pericardial,

vertebral, and viscera). See Figures 1.4, 1.5, 1.9, and 1.10.

3. Define regional and directional terms used in association with the

body (see Figure 1.4 and Table 1.1).

4. Understand anatomical and directional terms in relation to one

another.

5. Define mucous membranes and serous membranes. Identify the

following types of serous membranes: visceral and parietal layers of

the pleura, pericardial, and peritoneum (see Figure 1.10).

Discussion

Most people think of anatomy as the study of things you can see

with unaided vision. Although this is particularly true of the present

course, as Figure 1.1 in the text indicates, anatomy can pertain to the study

of structure at a variety of levels—from chemical through organism. We

will emphasize the study of cells, tissues (groups of similar cells that work

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together), organs (made up of two or more tissues) and systems (a

collection of organs with like functions).

Probably the most critical concept to grasp initially is that of the

anatomical position. It is illustrated in Figures 1.3 and 1.4. Note that it

consists of the body in standing position, head erect and forward, feet

shoulder-width apart, arms at sides, and palms forward. The terminology

that you will also learn in this unit is worthless if you do not know the

anatomical position. All of the terms are used in reference to the

anatomical position. Also, learn the regional terminology (1.4).

Next, study the directional terms in Table 1.1. As a self-test, cover

the definitions of terms and look at yourself in a mirror. See if you can

place each regional term on your own body correctly.

Also, try using the terminology to place body parts relative to one

another. For instance, the abdomen is ventral to the vertebral column.

(Note synonyms; I could have said that the abdomen is anterior to the

vertebral column.) Another example: the shoulder is proximal to the hand.

Try some of these out yourself.

Planes are hypothetical sheets that cut the body or anatomical

structures into two parts. As you can see in Figure 1.5, there are three

planes. The frontal plane cuts the body into front and back parts. The

transverse plane cuts the body into top and bottom parts. The saggital

(median) plane cuts the body into right and left parts. Often the parts that

a plane cuts the body into are equal halves, but this is not always true.

Body cavities are spaces that contain structures. The principal body

cavities you have to know are given in Figure 1.9. Note that the ventral

body cavity is further subdivided into thoracic and abdominopelvic.

Likewise, the dorsal body cavity is subdivided into the cranial cavity and

vertebral cavity. In turn, the thoracic cavity contains special spaces that

house the heart and accessory cardiac structures (pericardial cavity in the

mediastinum) and the lungs (two pleural cavities). Any structure found

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within the ventral body cavity is referred to as viscera. Thus, viscera labels

a category of organs which includes the heart, lungs, small intestines,

stomach, and so on.

Now turn to Figure 1.2 and study the placement of systems in the

body cavities. Some vital organs are exclusively located within certain body

cavities. Place the brain, spinal cord, heart, lungs, and digestive system

into body cavities for practice.

Mucous membranes are found lining tubes entering or exiting the

body. Mucous secreted onto these membranes serves a protective function.

For instance, the mucous membranes lining the nasal cavity and upper

respiratory tract trap inspired pollutants and pollens. Mucous membranes

also line the oral cavity and rectum.

Most of the organs in the ventral body cavity are completely or

partially covered by serous membranes. Serous membranes are double

layered and have an outer parietal layer and an inner visceral layer (see

Figure 1.10). The visceral layer actually adheres closely to the organ. The

layers are identified by organ, for example, the heart is surrounded by a

parietal pericardium and an inner visceral pericardium (see Figure 1.10).

The inner visceral layer actually adheres closely to the organ. The

layers are identified by organ; for example, each lung is surrounded by a

parietal plevia and a visceral pleura. A slight space between the two serous

layers contains serous fluid, which acts as a lubricant for the movements

made by organs when they are

active.

Sample Questions

Questions 1-7 require you

to identify planes or directions

indicated on the figure.

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Foils for Questions 1-7:


a. saggital b. transverse c. frontal d. cranial e. caudal f. lateral g. medial 1. This is the ______ direction.

2. This is the ______ direction.

3. This is the ______ plane.





8. Which of the following is incorrect about anatomical relations to the palm of the hand in the anatomical position? a. The palm is anterior to the dorsal surface of the hand. b. The hand is distal to the shoulder. c. The hand is medial to the abdominopelvic cavity. d. The hand is cranial to the thigh.

9. The lungs are located in this space.

a. dorsal body cavity b. abdominal cavity c. mediastinum d. thoracic cavity

10. What is the opposite of superficial?

a. lateral b. proximal c. internal or deep d. ipsilateral

Answers to Sample Questions

1. d; 2. e; 3. b; 4. c; 5. f; 6. g; 7. a; 8. c; 9. d; 10. c

In this course, you will submit your first assignment following Lesson 4.

Go on to Lesson 2.

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Lesson 2 Embryology

Reading Assignment

Read Chapter 3 in the text. Use the objectives listed below to guide

and focus your reading.

Objectives

1. Define the following: embryonic period, fetal period, blastocyst,

zygote, blastomere, cleavage, morula, amniotic sac, yolk sac, germ

layer, endoderm, ectoderm, mesoderm, notochord, neural crest,

somite.

2. Summarize developmental events during the first week of the

embryo, from fertilization to blastocyst.

3. Describe the formation of the three primary germ layers

(gastrulation) during week three of the embryo. Especially be able

to explain development of the nervous system (neurulation) from

neural plate to neural tube.

4. Summarize anatomical structures and tissues that are derived from

each of the primary germ layers.

5. Define the following common birth defects and their possible

etiologies: heart defects, mental retardation, spina bifida, Down's

syndrome, cleft palate, cystic fibrosis.

Discussion

Fertilization occurs in the distal (lateral) one third of the uterine

(Fallopian) tube of the female (see Figure 3.3). It results from the union of

an egg cell and a sperm cell, creating a new cell called a zygote. Soon after

fertilization occurs, the zygote begins to divide rapidly and form smaller

segments called blastomeres. This process of rapid cell division is referred

to as cleavage. By the time the dividing zygote nears the medial section of

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the uterine tube, it is known as a morula ("mulberry," ball of cells). The

morula is ready to begin the next phase of embryonic life, implantation.

The morula enters the uterus of the female about day four or five

following fertilization. In doing so the morula also begins to change its

internal anatomy (see Figure 3.4). Cells in the center begin to differentiate

(specialize) and form an inner cell mass (see Figure 3.3e). The remaining

space on the inside is represented by a space known as the blastocyst

cavity. The structure that was referred to as a morula when it entered the

uterus is now known as the blastocyst, with an inner cell mass and outside

cells known as the trophoblast.

The trophoblast cells on the outside of the blastocyst are

responsible for implanting the blastocyst into the uterine wall where it

may thrive in a nutrient rich environment until the fetal membranes can

fully develop and supply the growing infant with needed oxygen and

nutrients from the mother. The trophoblast accomplishes this task by

secreting powerful digestive enzymes that help the blastocyst "eat" its way

into the endometrium (inner layer of the uterine wall). As this process of

implantation occurs, note (see Figure 3.4) that the inner cell mass of the

blastocyst is beginning to change.

These changes signal the beginning of the next stage of embryonic

development, gastrulation. Gastrulation means cell movement, although

the process amounts to more than simply the movement of cells. By

around day nine (see Figure 3.4) the inner cell mass is made up of two

layers of cells, the epiblast and the hypoblast. The movement of cells of the

epiblast constitutes the process of gastrulation seen in Figure 3.5.

The beginning of the formation of the primary germ layers is

indicated by the appearance of the primitive streak, a raised groove on the

external surface of the epiblast (see Figures 3.5 and 3.6). The end result of

the process of cell movement will be the creation of a three-layered

embryonic disc in place of the earlier two-layered disc. The new three-

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layered disc will be comprised of the primary germ layers, the cells that

will form all of the structures that will become the infant.

Formation of the primary germ layers occurs when the cells of the

epiblast invaginate at the primitive streak in two successive waves. The

first cells to invaginate or "tuck under" become the endoderm and the

second group of cells invaginate to become the mesoderm. Cells that

remain in the original position of the epiblast cells become the ectoderm.

Figures 3.5 and 3.6 also demonstrate the formation of another

structure about the same time as gastrulation occurs, the notochord. The

notochord can be thought of as a precursor to the adult vertebral column.

But make certain to understand two things at this point:

1. The notochord is not part of the spinal cord, although it does

contribute to the formation of a structure found in the vertebral

column in adult life (the intervertebral disc).

2. The vertebral column is not the same thing as the spinal cord; the

latter is the nervous component housed within the vertebral

column.

However, the appearance of the notochord does correlate with the

development of the nervous system, derived from some of the cells of the

ectoderm. Figure 3.7 illustrates the process of neurulation, the formation

of the nervous system from the overlying ectoderm. Most of the process is

pretty obvious in Figure 3.7. Cells superior to the primitive node (the

swelling at one end of the notochord) differentiate and thicken, producing

a neural plate. The plate then deepens into a groove, which in turn folds

over itself, forming a neural tube. The superior extent of the neural tube

becomes the brain. The remainder develops into the spinal cord.

At the same time the neural tube is developing, cells immediately

lateral to the tube are pulled along with the deepening neural groove and

come to rest just lateral to the neural tube. These cells are referred to as

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the neural crests. They will develop into a number of structures, most

significantly, sensory nerves.

Weeks three and four in the life of the embryo are very busy, and

another important development is happening in conjunction with that of

the nervous system, differentiation of the mesoderm. The same Figure 3.7

that illustrates neurulation also shows movement and differentiation of

the mesoderm cells into three distinct groups. The first is the somites or

paraxial mesoderm. These cells reside close to the central axis of the

embryo near the notochord and the neural tube. Somites will contribute to

the formation of portions of the axial skeleton, the vertebrae and ribs, the

dermal layer of the skin, and much of the muscle system.

The intermediate section of the mesoderm forms some of the

organs in the ventral body cavity (e.g., kidneys, testicles, ovaries). The

most lateral portion of the mesoderm forms the cardiovascular system,

outer components of the digestive system, parietal membranes, and bones

and ligaments of the extremities.

In mentioning the adult structures that develop from the mesoderm

alone, the student might conclude that trying to keep straight which

structures develop from which of the three primary germ layers is a

daunting task. But there is an easier way to master the task than pure rote

memory. The trick when trying to remember any classification scheme

with two or more categories is to try to remember the easier categories

first. This means the number of categories to remember will be one less

than the total number. In the present case, there are three categories to

remember: ectoderm, mesoderm, and endoderm. I am suggesting that you

need only remember two of the three, as follows.

The ectoderm forms the outer layer of the skin (epidermis), the

nervous system, some bones of the skull and some glands. The endoderm

forms the inner walls of the digestive and respiratory systems, the lower

portion of the urinary system, and some glands. Everything else is formed

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from the mesoderm. So by process of elimination, you know what is

formed from the mesoderm without having to remember its derivatives in

a rote manner. Refer to Figure 3.10 for details of the structures formed

from each germ layer.

Hence, by the end of the embryonic period (0-2 months) almost all

of the necessary structures for survival are in place. The remainder of the

gestation is referred to as the fetal period. It consists primarily of growth

and maturation of structures put in place during the embryonic period.

Moreover, most serious birth defects (congenital defects) appear in the

embryonic period. It stands to reason that the problem will be more

serious if it develops earlier, since all subsequent structures are formed

from the three layers of the embryonic disc and its subsequent folding and

cell movement. In other words, the earlier a problem develops, the more

tissues that are affected, because the problem is perpetuated or passed

along into all structures formed from the affected structure.

Several examples of the more frequent birth defects are discussed in

the "A Closer Look" box at the end of the chapter. Although I will only

discuss one of those defects below, you should have a sense of which

embryonic structures are affected relative to each of the defects listed on

your objectives. Notice how many of the birth defects listed could be

avoided by living a healthy lifestyle and not abusing substances. Maternal

health is therefore crucial to the normal development of the infant.

Spina bifida in its most severe form is a neural tube defect. It results

from a failure of the distal/caudal end of the neural tube to close. The child

is born with a lesion called a "cele," most often found in the lower lumbar

or sacral areas. The resulting deficit is typically paralysis of both lower

extremities and incontinence. The child born with spina bifida may have a

problem with the cranial end of the neural tube as well and often presents

with a condition called hydrocephalus, "water on the brain." This problem

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as well as the paralysis resulting from spina bifida can be managed with

early detection and intervention.

Sample Questions

1. The morula forms as a result of this process. a. gastrulation b. neurulation c. implantation d. cleavage

2. Cells that eventually form the three primary germ layers are derived from this structure. a. trophoblast b. blastocoel c. embryonic disc d. notochord

3. Blood vessels form from this embryonic germ layer. a. ectoderm b. mesoderm c. endoderm

4. This term refers to cell movement. a. cleavage b. gastrulation c. neurulation d. implantation

5. Stem cells are derived from this structure in the embryo (you will have to research this one by reviewing the chapter closely). a. Inner cell mass b. trophoblast c. morula d. yolk sac


1. d; 2. c; 3. b; 4. b; 5. a

Go on to Lesson 3.

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UNIT 2 BASIC ORGANIZATION

Lesson 3 Cells

Lesson 4 Tissues

Written Assignment #1

Lesson 5 Integumentary System

Lesson 6 Bone and Skeletal Tissue Written Assignment #2

Examination #1

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Lesson 3 Cells

Reading Assignment

Read Chapter 2 in the text, focusing on material that pertains to

objectives listed below.

Objectives


1. Identify the structural components of a prototypical cell in an

illustration: plasma membrane, mitochondrion, endoplasmic

reticulum, golgi apparatus, nucleus, lysosome, centriole, ribosome,

and cytoplasm. See Figure 2.1.

2. List the functions of the cellular components in #1 above. Refer to

Figures 2.2, 2.5, 2.7, 2.8, 2.9, 2.10, 2.12, 2.13, 2.14, 2.15, 2.17, 2.18.

3. Identify the role of organelles involved in a secretion pathway

illustrated in Figure 2.8.

4. Generally, define the structure and function of a chromosome

(DNA).

5. Define mitosis, dysplasia, hyperplasia, hypertrophy, and necrosis.

Discussion

In the seventeenth century, Robert Hooke, an English physician,

was the first scientist to use the term "cells." Only later did scientists come

to fully appreciate the importance of Hooke's discovery. The cell is the

basic functional unit of the body. Like any of the larger functional units we

will study, it has a structure—it is an assembly of various parts.

The most basic of these parts is the cell or plasma membrane. The

cell membrane "marks off" the cell as an entity unto itself. It is essentially

a two-layered arrangement of phospholipids and proteins (see Figure 2.2).

This two-layered enclosure controls the entrance and exit of materials into

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and out of the cell proper. You should try to get a sense of the factors that

affect the permeability of the cell membrane (e.g., size of molecule). The

cell membrane can have special places on its outer surface, called receptor

sites, to interact with certain chemicals, such as neurotransmitters and

hormones.

Within the confines of the cell membrane, we find the remaining

parts of the cell: the structures called organelles and the fluid between the

structures, called cytoplasm. Cytoplasm is largely water, making it an

excellent medium for chemical reactions.

Starting with the nucleus, then, we will continue to study the

structure and function of the other parts of the prototypical cell. You

should continuously refer back to Figure 2.1 for study of the shapes of

organelles so that you can identify them later. Notice that small

illustrations for most organelles are found throughout the chapter.

The nucleus (Figure 2.13) is the "brain" of the cell. It almost

completely determines what the cell will do. It has its own membrane,

similar in structure to the general cell membrane. Within the nucleus we

find the genetic material of life, DNA (see Figure 2.14). It appears as

chromatin or chromosomes depending on whether the cell is actively

mitotic or not. DNA, RNA, and proteins are found in the nucleolus, a small

rounded body within the nucleus proper. (We will have more to learn

about DNA later.)

Ribosomes are sometimes called the "anvils" of the cell because

they are the sites where proteins are "forged" (assembled). Amino acids,

the building blocks of proteins, are brought to the ribosome for assembly

into a protein. Ribosomes can be attached or free. Attached ribosomes

appear as small dots (see Figure 2.6 for ribosomes attached to

endoplasmic reticulum) adhering to another structure, the endoplasmic

reticulum. Free ribosomes are just that—free-appearing in the cytoplasm

as unattached dots.

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Endoplasmic reticulum (Figure 2.5) appears as adjacent walls that

form channels, usually found close to the nucleus. If the endoplasmic

reticulum has ribosomes attached, it is called rough or granular

endoplasmic reticulum. If it does not have ribosomes attached, it is

referred to as a smooth or agranular endoplasmic reticulum. Endoplasmic

reticulum is sometimes specialized according to tissue type. For instance,

endoplasmic reticulum in muscle cells is specialized to facilitate

contraction and therefore given a special name—sarcoplasmic reticulum.

(The sarcomere is the functional unit in a muscle cell). The most

important functions of endoplasmic reticulum are storage and

transportation of various materials, but it also helps mechanically support

the cell because of its relatively substantial presence within the cytoplasm.

The golgi apparatus (Figures 2.7 and 2.8) is thought to work with

the endoplasmic reticulum and ribosomes to complete a network

responsible for a product, generally a protein, destined for secretion from

the cell. For instance, after the ribosome produces a product, the

endoplasmic reticulum transports it to the golgi apparatus. The golgi

apparatus then "packages" the product in a way that allows it to pass

through the cell membrane more easily. The golgi apparatus appears as a

stack of "pancakes" with globules floating away from it. The latter are

called secretory vesicles. Secretory vesicles might contain an enzyme to

help digest food, if the cell is in the stomach, or a different product if the

cell is located elsewhere in the body.

The nucleus, endoplasmic reticulum with ribosomes, and the golgi

apparatus, are linked together in cells that actively produce and secrete

useful products (e.g., digestive enzymes). Study Figure 2.8 to see how

these organelles work together in a secretion pathway.

The mitochondrion is often referred to as the "powerhouse" of the

cell because it is responsible for synthesizing energy for the cell's use in the

form of ATP. (ATP molecules can be thought of as batteries.) As can be

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observed in Figure 2.10, the mitochondrion looks like an oblong capsule or

coated tablet on the outside. But on the inside, viewed in the cut-away

portion of Figure 2.9, the mitochondrion has many convolutions or

"shelves" known as cristae. These shelves are produced when the inner

membrane of the mitochondrion folds onto itself. This folding

exponentially increases the surface area for reactions, and hence, energy

formation. (By the way, such folding is a good example of how function is

facilitated by structure.) Because of their involvement in energy formation,

you might logically suppose that very active cells would contain many

mitochondria. This is precisely the case. For instance, muscle cells contain

many mitochondria.

Lysosomes are round structures with fairly thick membranes to

hold their contents—powerful enzymes with the potential to destroy the

cell itself. They are also produced by the golgi apparatus. Lysosomes are

not smooth spheres; rather, their surface is irregular and uneven. Because

of their contents, lysosomes are sometimes called the "suicide packets" of

the cell. More often, however, in the healthy cell, the lysosome can destroy

unwanted invaders that pose a danger to the integrity of the cell or ingest

other "worn out" cellular organelles. For instance, white blood cells

(leukocytes) contain many lysosomes.

Centrioles are long, narrow cylinders located within a greater

structure called a centrosome (see Figure 2.12). Centrioles arrange

themselves in a very organized fashion, appearing as nine evenly spaced

bundles of microtubules. Viewed from the side (Figure 2.12c), the

microtubules of the centriole look like spokes in a wheel. Centrioles are

active in the process of mitosis (cell duplication). They seem to assist in

the movements of chromosomes during mitosis.

DNA is frequently studied in its highly organized state, in the form

of a chromosome, a state it assumes just prior to and during cell division.

DNA looks like a ladder that has been twisted. This is often called a double

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helix arrangement of DNA. The vertical portions of the ladder are

composed of repeating sequences of sugars and phosphates (Figure 2.14).

The horizontal parts of the ladder, where one might place a foot, are made

up of two nitrogen bases. There are four different bases (see "C," "G," "A,"

and "T" in Figure 2.14) in all and the ways in which these bases are

matched up form a sort of code or blueprint for the formation of proteins

and RNA. This is accomplished by portions of the DNA molecule

unraveling and fresh bases being matched up or paired with those

exposed. Accordingly, specific lengths of the DNA molecule correspond to

specific proteins or types of RNA. Lastly, when the entire DNA molecule

unravels, it can completely replicate itself. This happens just before

duplication of the entire cell during the process of mitosis.

Mitosis (Figure 2.18) is the type of cell division that results in two

new/daughter cells that are identical to the parent cell—each has the exact

same 23 pairs of chromosomes. Mitosis is necessary for growth and

development early in life, and for maintenance of tissues the remainder of

life.

Interphase is basically the time in a cell's life between mitotic

divisions (see Figure 2.17). Mitosis consists of four phases that result in the

formation of two daughter cells genetically identical to the parent cell.

Interphase and mitosis are summarized in Figure 2.17.

During interphase the cell is preparing for cell division as well as

carrying on its normal functions. The cell grows and synthesizes an

identical set of DNA for use in the subsequent division. As you can see in

Figure 2.17, interphase takes quite a long time compared to all four of the

phases that make up mitosis.

You do not need to know the details of mitotic division. You should

be able to define mitosis and explain its importance for growth and

maintenance.

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Look up definitions of terms listed in the final objective at the end

of the chapter. Also, look over the "A Closer Look" window at the end of

the chapter, which discusses cancer, and read the short section on aging.

Sample Questions

Try to answer the questions below after you have read Chapter 2,

satisfied the objectives, and studied the figures indicated. Use the

questions as a self-test. If you miss some of the questions, go back to the

chapter to study the material again and find out why you missed the

question.

1. Name the organelle associated with packaging and secreting materials from the cell. a. golgi apparatus b. mitochondrion c. lysosome d. nucleus

2. Where would you expect to find the most ATP? a. in the cell membrane b. in the DNA molecule c. in the mitochondrion d. in the chromosomes

3. Name the structure whose spherical, external surface is irregular; it contains enzymes strong enough to destroy the entire cell. a. centriole b. nucleus c. golgi complex d. lysosome


1. a; 2. c; 3. d

Go on to lesson 4.

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Lesson 4 Tissues

Reading Assignment

Read Chapter 4 and pages 125-126 in your textbook with emphasis

on the topics covered by the objectives below.

Objectives


1. Define a tissue and describe four basic tissue types.

2. Identify the functions of epithelium. Contrast the general

characteristic of epithelium with the general characteristics of

connective tissue: proportion of matrix, proportion of cells, vascular

supply, basement membrane, embryonic derivative, location.

3. Briefly list the structure and function of simple, stratified, pseudo-

stratified, transitional and glandular epithelium (Figure 4.3).

4. Identify the four types of adult connective tissue (CT proper,

cartilage, bone, blood) and describe the following structures found

in loose (aveolar) connective tissue (Figure 4.11): fibrocytes,

collagen fibers, elastic fibers, reticular fibers, and ground substance

or matrix.

5. Compare and contrast the different types of connective tissue:

connective tissue proper, cartilage, bone, and blood (see Figures

4.9, 4.12).

6. Describe the inflammatory response and repair process; identify the

four classic symptoms of the inflammatory response.

Discussion

A tissue is a group of similar cells that work together to accomplish

a common purpose. We will spend considerable time later in this course

studying two of the four basic tissue types—muscle and nervous tissue.

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The remaining types of tissue are epithelial and connective. Histology is

the study of structure and function of tissues. For now, you should get a

general sense of how to discriminate between the four tissue types. Most

people have difficulty discriminating epithelial and connective tissues, so

we will spend most of the time in this lesson focusing on those two tissue

types.

Basically, epithelial tissue does two things. It covers things

(covering/lining epithelium) or it forms glands. Regardless of the type,

epithelium has some definite characteristics you can use to distinguish it

from connective tissue. These include: tightly packed cells, little

intercellular substance (called matrix), a basement membrane (that

supports epithelium), derived from all three layers of the embryo

(ectoderm, mesoderm, endoderm) and no direct blood supply (avascular)

(see Figures 4.1–4.2).

Covering or lining epithelial tissue can be further sub-divided on

the basis of the number of layers of cells and whether or not all of the cells

reach the surface or not (see Figure 4.3). Simple epithelium means there is

a single layer of cells (classified by shapes: squamous, cuboidal,

columnar), whereas stratified epithelium has several layers of variously

shaped cells. The former are found in areas where there is little wear and

where materials have to move into and out of channels easily (like the

lining of capillaries of the vascular system). The latter, stratified-type of

epithelium is found in areas that experience considerable wear and tear

(skin, bladder, and some parts of the digestive tract). A specialized type of

stratified epithelium is known as transitional. It is specialized to distend

(stretch). The third general type of epithelium is called pseudostratified

(pseudo means "false") epithelium (see Figure 4.3d). This is because the

cell arrangement looks like it has several layers, but in reality there is only

one layer of cells. The pseudostratified appearance is attributable to the

fact that not all of the cells reach the lumen of the channel they line.

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The second term that is used to label an epithelial tissue (e.g.,

squamous) refers to the cell shape. The various types of epithelium are

illustrated in Figure 4.3. But you are only expected to know the

significance of simple, stratified, or glandular epithelium; you do not have

to know cell shape.

Glandular epithelium comprises both types of glands, exocrine and

endocrine. For now, you simply need to know that endocrine glands

always secrete hormones; exocrine glands never secrete hormones

(although their products are useful). We will discuss glands in more detail

in the lesson on the endocrine system.

Connective tissue can be discriminated from epithelium on the

basis of its rich vascular supply (with the exception of adult cartilage and

ligament), widely separated cells, and substantial intercellular substance

(matrix). Connective tissue is derived exclusively from the mesoderm of

the embryo. Connective tissue does not cover or line, rather it occurs

beneath the surface, deep to covering or lining epithelium. However, the

connective tissue category probably represents a rather surprising

collection of structures that are seemingly unrelated. Bone, cartilage,

tendons, ligaments, and blood are all categorized as connective tissue.

However, they all share in common the characteristics of connective tissue

with respect to vascular supply, cell to intercellular matrix relationship,

embryonic derivative, and location (see Figure 4.9).

For now, we will look at loose (areolar) connective tissue as the

prototypical connective tissue and see what it is made of. Fundamentally,

the remaining sub-types of connective tissue are differentiated on the basis

of fiber types and amounts, cell types, and consistency of matrix. The

matrix of loose connective tissue is composed of a viscous ground

substance. In its normal state, ground substance facilitates the movement

of materials through connective tissue.

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The matrix also includes fibers, mostly collagenous, with some

elastic. As suggested earlier, the amount and type of fiber helps determine

the type of connective tissue. For example, if there is a large amount of the

collagenous fiber type, with very little fluid between, the connective tissue

is likely a tendon or ligament. Collagen fibers are very tough and resist

stretching. Elastic fibers are tough and can be stretched (hence the title

"elastic"). Finally, reticular fibers are often associated with soft organs

(like the liver) where they provide a framework or structure for the organ.

The typical cell of loose connective tissue is the fibroblast/fibrocyte

(see Figures 4.9 and 4.11 and Table 4.2). Authorities believe that fibrocytes

are responsible for production of many of the fibers of loose connective

tissue and the ground substance of the matrix.

Several other cells (macrophages, plasma cells, mast cells, various

white blood cells) can be found in loose connective tissue. Their primary

responsibility is defense of the body against disease and infection. The

placement of these cells that comprise part of the body's immune response

makes sense since they serve to form a second line of defense if a "germ"

finds access to the body through a cut that penetrates the epidermis.

Loose connective tissue is only one of several types of connective

tissue proper. The others are dense regular, dense irregular, elastic,

reticular, and adipose. Each is specialized according to the amount and

types of fibers found in the matrix.

Dense connective tissue is dominated by collagen fibers (Figure

4.12). If the collagen fibers line up in parallel rows, then it is dense regular

connective tissue. This type of connective tissue is characteristic of

ligaments and tendons, where a lot of strength is needed in one direction.

If the fibers run in various directions, then it is dense irregular connective

tissue. This is characteristic of the dermis layer of the skin (covered in the

next lesson) the periosteum of bone, and the capsules surrounding

synovial joints.

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Reticular connective tissue (Figure 4.12) is understandably

dominated by reticular fibers. Reticular fibers are capable of forming a

framework or "scaffold" for other tissues to attach to. This is why reticular

connective tissue characteristically forms the structural part (stroma) of

many soft organs, such as the liver, spleen, and lymph nodes.

Elastic connective tissue (Figure 4.12) can be found in large arteries

near the heart that experience a lot of stretching when blood is forcefully

ejected into them from the right or left ventricle. Elastic connective tissue

can also be found in ligmentum flavum between the lamina of two

vertebrae where considerable stretching occurs. As you might have

deduced, elastic connective tissue is distinguished from others by virtue of

its generous compliment of elastic fibers.

Adipose tissue (see Figure 4.12) is made up of fat cells (adipocytes)

and is designed for storage of fat droplets within the cytoplasm of the fat

cells.

Mature cartilage distinguishes itself from connective tissue proper

in several ways. First, unlike most connective tissue, cartilage does not

receive a good vascular supply. Second, the typical cell found in cartilage is

a chondrocyte and not a fibrocyte as in connective tissue proper. Finally,

the matrix of cartilage is semi-solid and less fluid than that of loose

connective tissue.

Cartilage comes in three varieties (see Figures 4.12 and 6.1). First

and most plentiful is hyaline cartilage. Hyaline cartilage makes up the

embryonic skeleton, the costal cartilages running from the ribs to the

sternum, and it covers the articular surfaces of bones as they enter into

joints.

Fibrocartilage is considerably less plentiful. It is found between

vertebrae as the outer ring of intervertebral disks, between the two pubic

bones of the bony pelvis as the symphysis pubis, and within some joints as

articular discs (e.g., menisci of the knee).

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The last type of cartilage is elastic cartilage. It is found in only a few

places as well. Elastic cartilage comprises the epiglottis that covers the

trachea as you swallow so that food does not find its way into your trachea

("windpipe"). It also makes up the auditory (eustachian) tube and the

external ear. Hence, you can distort and bend the external ear and it will

return to its original shape.

Bone (see Figure 4.12) is also a type of connective tissue that we will

discuss in another lesson. Like all other connective tissue, it has only a few

cells (osteocytes) scattered in a matrix with collagen fibers. Everyday

observation confirms that a major difference between bone and other

types of connective tissue is that the matrix of bone is solid. This is

because of the deposition of minerals between the osteocytes.

Likewise, blood is also considered connective tissue because it

shares the same features. It has a few cells, erythrocytes and leukocytes,

scattered among a large amount of intercellular matrix called plasma.

Figure 4.9 summarizes the development of all of the types of

connective tissue from the embryonic mesenchyme (mesoderm).

The remaining two tissue types are muscle (Figure 4.14) and nerve

(Figure 4.15). Muscle is specialized to shorten (contract), whereas nervous

tissue is specialized to conduct nerve impulses from place to place. Muscle

and nervous tissue are important enough to warrant in-depth coverage

later in this course.

For now, muscle tissue is found in three types. Skeletal muscle

moves the skeleton. Cardiac muscle is found in the middle wall of the

heart. Smooth muscle comprises the muscular layer of the walls of various

tube-systems (viscera), such as the vascular system.

Nerve tissue is divided into the central nervous system (brain,

spinal cord) and peripheral nervous system (peripheral nerves). It is

specialized to transport "information" we know as a nerve impulse.

A- 36


Sample Questions

Make sure you have read the material thoroughly and satisfied the

objectives at the beginning of this lesson before attempting the sample

questions. Try the questions without the aid of book or notes. If you miss a

question, go back and try to determine why you missed it.

1. Which of the following is not a type of epithelial tissue? a. simple epithelium b. cartilage c. stratified epithelium d. exocrine gland

2. Which cell is typically found in loose connective tissue? a. chondroblast b. fibroblast c. osteoblast d. mesenchymal

3. Which statement best describes epithelium? a. It is always arranged as a single layer of cells. b. It contains a large amount of matrix. c. It has an abundant blood supply. d. It has a free border.

4. Tearing a ligament would mean you have sustained damage to this type of tissue. a. epithelial tissue b. connective tissue c. muscle tissue d. nervous tissue

5. A group of cells operating together to perform a specialized activity is called by this name. a. organ b. system c. organism d. tissue


1. b; 2. b; 3. d; 4. b; 5. d

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Instructions

Instructions for submitting assignments electronically in the ICON

Drop Box are posted on the ICON course site under "Submit

Assignments."

Description

This assignment is worth 10 points.

Organs are defined as structures that are made up of more than one

tissue. This means that tissues in organs work cooperatively with one

another to accomplish necessary tasks. This assignment is intended to

help you appreciate the cooperative relationships among tissues within

organs, specifically the skin and muscles (both are organs and systems).

Answer all three of the questions below for this assignment.

1. Any given skeletal (voluntary) muscle qualifies as an organ.

Therefore, a cross section through a muscle such as the biceps

brachii would reveal two or more tissue types. In fact, all four of the

basic tissue types are represented in the biceps brachii. Explain,

specifically, where each of the four tissue types is found within the

biceps brachii. (Hint—remember the muscle will have blood supply,

nerve supply, and a means to attach to a bone to produce

movement).

2. Skin (the integument) affords the student an excellent opportunity

to study how epithelial tissue and connective tissue work in

cooperation. One of the major functions of the skin is protection.

Explain how the epithelial portion of the skin (epidermis) and the

connective tissue part of the skin (dermis) serve to protect the

individual.

3. Epithelial cells are the frequent origins of several types of cancer

(e.g., skin cancer, lung cancer, …). Explain why this is the case.

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Identify and explain the attribute of epithelial tissue that is

associated with cancer and how this very same attribute is

beneficial to humans as they age.

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Lesson 5 Integumentary System

Reading Assignment

Read Chapter 5 in the text, paying special attention to answering

the objectives specified below.

Objectives


1. Define and describe the skin as an organ, and the integumentary

system.

2. Know the functions of the integument.

3. Identify cells typically found in the epidermis, including:

keratinocytes, melanocytes, Langerhans cells, Merkel cells.

4. Identify the layers of the integument and the types of tissues,

structures, and cells found in each layer: epidermis, dermis,

hypodermis/subcutaneous.

5. Define keratin.

6. Describe the following clinical applications: burns (first, second,

third degree, rule of nines), skin cancer.

Discussion

The skin is the largest organ in the body, comprising about seven

percent of a person's total body weight. Including its accessory structures

(hair, nails, …), the skin is also considered a system, the integumentary

system. A system is nothing more than a group of organs working in

common to perform specific functions. However, we will focus on the skin

as an organ within the integumentary system. (Recall that an organ is a

group of tissues that work together to perform common functions.)

The skin as an organ serves a very important protective function for

the body. Mechanical protection is afforded by the outer layer of the skin,

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which is composed of stratified epithelium. Melanocytes in the epidermis

darken the skin upon excessive exposure to UV radiation (sunlight) to

protect deeper structures (blood vessels, red blood cells) from damage.

Finally, cells responsible for defending the body (e.g., white blood cells)

are found in the dermis of the skin to protect against invading germs.

The skin also helps greatly with the regulation of temperature and

receives important sensory information through several general sensory

receptors (e.g., touch, temperature, pressure, pain). Although these are the

primary functions of the integument, you should take note of the

remaining functions: preventing excessive loss of fluid, storage, excretion,

and synthesis of Vitamin D.

As it turns out, the skin is comprised primarily of two tissues we

just studied (in Lesson 4) in some detail. The outer layer of the skin is

comprised of epithelial tissue and called the epidermis, while the middle

layer is connective tissue called the dermis.

The epidermis of the skin is stratified, as you might have expected,

because the skin is a "covering" that experiences considerable wear and

tear. Figures 5.1 shows the epidermis in more detail. As can be seen, it is

comprised of four layers of epithelial cells (Figure 5.3).

Starting with the deepest layer of epidermis we find stratum basale.

Cells of the basale are capable of mitotic division and, hence, serve to

replenish more superficial cells of the epidermis as they are shed via the

wear and tear process.

The stratum spinosum overlies the basale and together with basale

are collectively labeled the stratum germinativum. Spinosum is also

involved in the production of replacement cells for more superficial layers

of the epidermis.

Stratum granulosum represents the first layer of epidermis where

cells are no longer duplicating. Granulosum is active in producing a

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protective "waterproofing" substance for the skin called keratin. Hence,

the outer layer of skin is sometimes referred to as keratinized epithelium.

Stratum lucidum (not shown in Figures) is found only on hairless

surfaces, such as the palmar aspect of the hand. Like granulosum, lucidum

is also involved in keratin production.

The outermost layer of the epidermis is the stratum corneum.

Corneum consists of many rows of dead cells that are progressively

sloughed as they move to the surface. Corneum's many layers are crucial to

satisfying the protective function of skin, even though the cells are dead.

The typical cell of the epidermis is a keratinocyte; it comprises the

multiple layers of epithelium that constitute the epidermis. Melanocytes

are also found in the epidermis. Melanocytes secrete melanin, which

contributes to the pigmentation of our skin. The dark melanin pigment

affords protection for deeper structures against excessive exposure to

ultra-violet radiation from the sun. A third type of cell found in the

epidermis serves a protective function by way of its phagocytic property; it

is called a Langerhans cell. Finally, Merkel cells are thought to serve as

sensory receptors for touch.

The second layer of the skin is known as the dermis (Figure 5.1).

The dermis is considered connective tissue, characterized by a good

vascular supply, more matrix, and fewer cells. Like the epidermis more

superficially, the dermis is layered. Unlike the epidermis, however, it has

only two layers—the papillary and reticular layers.

The papillary layer of the dermis is directly deep to the stratum

basale of the epidermis and sends finger-like projections up into the

epidermis at somewhat regular intervals. These projections are called

dermal papillae. Sometimes the papillae contain sensory receptors for

touch or pressure and capillary loops to bring blood close to the epidermis

(see Figure 5.1). Loose connective tissue is characteristic of this region.

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The reticular layer of the dermis is far thicker and more extensive

than the papillary. This layer contains many glands, like sweat glands, and

nerves running to sensory receptors and to the smooth muscle structures

in the skin. Dense irregular connective tissue is typical of this part of the

dermis.

The final layer is the hypodermis. It contains adipocytes (fat cells)

and loose connective tissue. The hypodermis is the location where excess

fat is frequently stored.

You should skim the remaining portions of the chapter, taking note

of the blood supply to the skin, epidermal derivatives (hair, nails, etc.) and

the different types of exocrine glands found in the skin (sweat and oil

glands primarily). You might find the section on the effects of aging on the

skin and the effects of excessive sun on the skin particularly interesting.

Burns are thermal trauma to one or more layers of the skin (see

Figure 5.11). Burns are graded according to the depth of the skin damaged.

First degree burns affect only the epidermis. Second degree burns damage

the epidermis and part of the dermis. The most serious third degree burn

damages the entire depth of the skin. The most serious acute problem for

the burn victim is excess fluid loss which may lead to life threatening

shock. Until the skin has repaired itself, the long-term problem is risk of

infection. The "rule of nines" is used to determine the extent of trauma

associated with burns. Consult Figure 5.11 to determine how to apply the

rule of nines.

Read the section at the end of Chapter 5 that pertains to cancer.

Sample Questions

1. How many different layers were defined within the epidermis? a. 1 b. 3 c. 5 d. 7

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2. Which of the following types of epithelium is characteristic of the skin?

a. simple b. stratified c. collagenous d. pseudostratified

3. Regeneration of the epidermis is largely the function of which of the

following stratum? a. corneum b. lucidum c. granulosum d. germinativum

4. Which of the following is the deepest layer of the epidermis?

a. papillary b. corneum c. reticular d. basale

5. Merkel cells are found in this layer of the skin.

a. epidermis b. dermis (papillary region) c. dermis (reticular region) d. hypodermis (subcutaneous layer)


1. c; 2. b; 3. d; 4. d; 5. a

Go on to Lesson 6.

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Lesson 6 Bone and Skeletal Tissue

Reading Assignment

Read Chapter 6 in your textbook. Again, take special note of those

sections most pertinent to answering the objectives listed below. You will

notice the objectives from this lesson on will generally be more numerous

and detailed.

Objectives


1. Describe the components and functions of the skeletal system.

2. Identify and give examples of each of the four shapes of bones (see

Figure 6.2).

3. Diagram a long bone; identify each part and describe its functions

(see Figure 6.3).

4. Describe a cross-section through the diaphysis of a long bone,

noting periosteum, compact bone and components of an osteon,

endosteum and medullary cavity (see Figure 6.6). Contrast compact

bone with spongy bone.

5. Describe the process of endochondral ossification (Figure 6.10).

Contrast endochondral ossification with intramembranous

ossification.

6. Briefly explain how bones grow in length and the role the

epiphyseal plate plays in this process.

7. Generally describe remodeling of bone and the role of osteoclasts in

the process.

8. Describe the process of fracture repair.

9. Define and list risk factors for osteoporosis.

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Discussion

Common sense tells us bone tissue protects and supports. But some

of bone's other functions are rather surprising. For instance, bone is a

major reservoir for minerals. This means that the body might sacrifice a

share of bone tissue in order to maintain adequate levels of some minerals,

such as calcium. In fact, the presence of acceptable levels of blood calcium

is absolutely necessary for life. Bone is also involved in blood cell

production (hemopoiesis). Of course, bones also give muscles something

to hang onto, and as a consequence, act as levers to produce movement.

As we noted earlier, bone is one type of connective tissue. It is well

supplied with blood vessels, has few cells (osteoblasts, osteocytes,

osteoclasts) and a great deal of matrix in between the cells. The difference

between bone and other types of connective tissue is that the matrix is

hardened via the deposition of minerals, a process called calcification. Like

most other connective tissues, bone has fibers (collagenous) too.

Identify the four basic bone shapes in Figure 6.2: long, short, flat,

and irregular. Long bones are commonly found in the extremities. Flat and

irregular bones tend to be found in the axial skeleton.

At this point you should turn to Figure 6.3, showing a prototypical

long bone. You need to be able to draw a long bone and label the parts, just

as you see them in Figure 6.3.

After you are able to visually recognize the parts of a long bone, turn

your attention to the function of each part. First of all, the diaphysis and

epiphysis essentially have no function other than being names we use to

identify certain regions on the surface of a long bone. However, the

remaining structures you identified in Figure 6.3 are of considerable

functional significance. Hence, you should learn the functions of these

structures well.

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As you may have surmised from our work with the prototypical long

bone, bone tissue proper takes two basic forms—compact and spongy. In

turn, each of these types of bone has its own unique organization. In

compact bone, the basic structural unit is called an osteon; in spongy bone,

the basic structural unit is the trabecula.

In Figure 6.6, an osteon of compact bone can be seen as it is

organized around a blood vessel. The osteon reminds some people of the

growth rings that can be seen in the trunk of a felled tree. The calcified

matrix appears as a series of layers (concentric lamellae). Between each of

the layers you can see little spaces called lacunae. Inside each lacuna is a

mature bone cell (osteocyte). Finally, notice the small processes radiating

out from each of the lacunae; these are called canaliculi. The canaliculi are

actually channels that are necessary for essential nutrients and oxygen to

reach the osteocytes that are isolated in the lacunae.

Spongy bone can be seen at the epiphyseal ends of long bones and

the endosteum that lines the medullary cavity (see Figure 6.3) and in the

center of flat bones, such as those of the skull (see Figure 6.4). Spongy

bone is much more porous than compact bone and does not organize into

osteons. The structural unit of spongy bone is called a trabecula

(trabeculae is plural). The trabecula takes quite a different form than

compact bone; it is organized into an open lattice-work type of

arrangement. The blood supply is more direct, as blood circulates rather

freely throughout endosteum bone. Thus, you will not find canaliculi in the

trabeculae of spongy bone.

Bone formation (ossification) can take two different routes.

Intramembranous ossification is the more direct of the two, wherein bone

is formed directly from a fibrous membrane (Figure 6.9). More commonly

though, bone (especially long bones) is formed from cartilage. Do not

make the mistake of thinking the former process results in spongy bone

and the latter in compact bone. No structural difference results from the

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two distinct ossification processes. That is, both result in spongy bone and

compact bone.

For the most part, only bones of the skull are formed through

intramembranous ossification. The majority of bones are formed through

the second type of ossification that begins with a cartilage model of the

future bone. This process is called endochondral (within cartilage)

ossification and is diagrammed in Figure 6.10. After the cartilage model is

laid down in the embryo, some cells in the perichondrium become

osteoblasts. At the same time the cells and matrix in the center of the

diaphysis of the cartilage model breaks down, leaving large cavities

(known as cavitation of the model). Next, a periosteal bud penetrates the

diaphysis of the model delivering bone cells secreting osteoid in the center

of the diaphysis. This is the primary ossification center. The future

medullary cavity develops when osteoclasts break down some of the bone

tissue in the center of the diaphysis to create a space.

Next, secondary ossification centers appear at each epiphyseal end

of the bone. The process leading to the formation of the primary

ossification center in the diaphysis is repeated in each epiphysis.

The problem is how to accommodate growth in length and width of

the bone until the individual reaches adulthood. As it turns out, cartilage

persists in the epiphyseal growth plate, located between epiphysis and

diaphysis. (The growth plates have five zones of cartilage; see Figure 6.11.)

The cartilage cells here continue to be actively mitotic and continue to

produce matrix. The cartilage cells and matrix on the epiphyseal side of

each growth plate divide, pushing some cells toward the diaphysis.

Eventually, these cells are calcified, then break down. The remnants of

calcified matrix project into the medullary center of the diaphysis.

Osteoblasts from the diaphysis then adhere to these calcified "stalagtites"

and deposit bone tissue on the remains. Hence, cartilage cells are laying

down matrix on the epiphyseal side of each growth plate while bone is

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eventually replacing cartilage on the diaphyseal side of each growth plate.

This is the way bones increase in length.

Eventually, the process ceases when all the cartilage in the growth

plate is replaced by bone tissue. At this point the epiphyseal plates are said

to be "closed" and the person reaches final adult stature.

Remodeling is accomplished by new bone tissue being laid down on

the periosteal (outer) surface of the diaphysis and being destroyed

(resorbed) on the endosteum (inside) side of the diaphysis. Osteoclasts are

the cells responsible for resorbing bone tissue closest to the medullary

center. As a matter of fact, this process (called remodeling) continues

throughout life and assures that as bone is worn out it will be constantly

replaced. Osteoblasts and osteoclasts that are found in both the

periosteum and endosteum also remodel the bone surfaces.

The process of fracture repair is summarized in Figure 6.14. It

consists of three basic steps: formation of the fracture hematoma (blood

clot), callus formation (cartilagenous and bone), "bridges" over the two

fractured ends. Finally, the fractured area is remodeled and the original

bone is restored.

Osteoporosis is loss of the mineral content in bone tissue in excess

of what might be expected as a result of the normal aging process. The

problem is—why is bone tissue lost? Is it because osteoblasts become less

active; because osteoclasts become more active; or something else? (You

can dig out the answer to this one yourself.) Moderate exercise is thought

to retard the loss of mineral content in bone tissue because it places

optimal stress on bones. The body, in turn, accommodates to stressors and

this may explain why regular exercise tends to be associated with

preserved mineral content in bone. (And you thought exercise was only

good for your muscles and cardiovascular system!)

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Sample Questions

Test yourself with the following questions after you feel comfortable

with the material in Lesson 6. Make sure you check out the questions you

miss.

1. A fracture in the shaft of a bone would be a break in this part of a long bone. a. epiphysis b. periosteum c. diaphysis d. articular cartilage

2. The growth of a long bone in length occurs in this location.

a. epiphyseal plate b. articular cartilage c. periosteum d. center of the shaft

3. Remodeling of a bone is a function of these two cells.

a. chondrocytes and osteocytes b. osteoblasts and osteocytes c. osteoblasts and osteoclasts d. chondroblasts and osteoclasts

4. Name the bone that belongs to the axial skeleton.

a. clavicle b. scapula c. pelvis d. sacrum

5. Identify a bone from those below formed by intramembranous

ossification. a. humerus b. femur c. tibia d. mandible


1. c; 2. a; 3. c; 4. d; 5. d

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Instructions



Assignments."

Description


1. Discuss the similarities and differences between loose connective

tissue, dense (regular and irregular) connective tissue, and bone.

2. Define the parts of a long bone and list the functions of each part.

3. Describe the major events of endochondral ossification (use Figure

6.10 to help organize your answer). Begin with formation of the

cartilage model in the embryo.

Examination #1

Examination #1 follows written assignment #2. This will be a one-

hour, supervised examination, covering material in Lessons 1 through 6.

No books, notes, or other aids may be brought to the exam. The

examination consists of forty multiple-choice questions of the same type

you have seen in the sections of sample questions in each lesson, according

to the number of objectives per topic.






version only).

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UNIT 3 MOVEMENT

Lesson 7 The Axial Skeleton

Lesson 8 The Appendicular Skeleton

Lesson 9 Joints


Lesson 10 Muscle Tissue

Lesson 11 Muscle System


Examination #2

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Lesson 7 The Axial Skeleton

Reading Assignment

Read Chapter 7 in the textbook. As before, use the objectives to

guide your reading.

Objectives


1. Categorize bones into either axial or appendicular skeleton (Figure

7.1)

2. Identify the 22 bones of the skull (8 cranial and 14 facial) and

selected landmarks—mastoid process, styloid process, occipital

condyles, foramen magnum, sella turica, cribiform plate, crista galli

(Figures 7.2, 7.3, and 7.4).

3. Locate and identify the hyoid bone (Figure 7.12).

4. Describe the structure of a typical vertebra (Figure 7.15). Identify

the unique features of cervical, thoracic, lumbar, and sacral

vertebrae (Figures 7.16–7.18)

5. Identify the normal curvatures of the spine (Figure 7.13). Which are

primary and which are secondary?

6. Identify and describe the sternum (3 parts) and ribs (true, false,

floating). Explain how the ribs articulate with the sternum and the

vertebral column. (Figures 7.19–7.20)

7. Identify bones and landmarks that form the following joints: typical

intervertebral joint, atlanto-occipital joint, atlanto-axial joint, joints

between rib and vertebra, ribs and sternum, sacrum and ilium.

8. Describe the following impairments: kyphosis, lordosis, scoliosis

and herniated disc (Figure 7.14).

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Discussion

Study Figure 7.1 and be able to classify bones into either the axial or

appendicular skeleton. Bones of the axial skeleton lie along the mid-line or

central "axis" of the body, whereas bones of the appendicular skeleton are

associated with the upper and lower extremities.

The tough part of this lesson and the one that follows will be

disciplining yourself to study the diagrams and learn the bones and

markings listed in the objectives above. The best first step is to review the

bones of the appendicular skeleton versus the bones of the axial skeleton

in Figure 7.1. You will probably want to use this figure quite often to test

yourself. (Remember, anatomy is very visual, so you will have to spend a

lot of time on the illustrations.)

Next, identify the bones of the skull and the landmarks listed in

objective number 1 (Figures 7.2, 7.3, 7.4). The toughest one to picture is

the ethmoid in Figures 7.3 and 7.7. It is a plate of bone pretty much in the

saggital plane, situated directly posterior to the nasal bones. This makes it

difficult to see on almost any superficial view of the skull, though you can

see the superior part of it in the view of the cranial floor in Figure 7.4c (it is

labeled the cribiform plate).

The vertebral column consists of thirty-three individual vertebrae:

seven cervical, twelve thoracic, five lumbar, five sacral (fused) and four

coccygeal (also fused). There are also four normal curves in the vertebral

column throughout its length (see Figure 7.13). Thoracic and sacral curves

are primary (present at birth) and anteriorly concave (curved part

forward), while cervical and lumbar curves are secondary (develop after

birth) and anteriorly convex. Take note of the fact that all normal vertebral

curves are in the saggital plane. No curves are observed on an anterior

view of a normal adult vertebral column.

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Next, study the vertebra in Figure 7.15. Be able to identify all the

parts in a superior view indicated in your objectives. Also note that when

two vertebrae are set one on top of the other a foramen is formed between

two adjacent pedicles. This is called the intervertebral foramen and it is

the route of exit for spinal nerves from the spinal cord. As you can see in

Figure 7.13, when vertebrae are stacked one atop another, they form joints.

These so-called intervertebral joints are slightly movable and allow for

subtle posture adjustments.

You will notice that at each level, the vertebrae take on some very

specialized shapes to do their jobs better. Figures 7.16 through 7.17 will

visually reinforce the differences and similarities between cervical,

thoracic and lumbar vertebrae. Table 7.2 summarizes the important

differences between vertebrae.

The cervical vertebrae are probably the most distinct. C1 (atlas)

vertebra, for instance, is simply a ring of bone with two very large superior

articular facets to receive the occipital condyles (thus forming the

atlanto-occipital joint). The C2 vertebra, or axis as it is sometimes

called, has a distinctive superiorly directed process called the dens. The

dens as well as the superior articular facets of C2 articulate with C1 to form

the atlanto-axial joint. The vertebra prominens, or C7, is palpable if you

reach around behind yourself, flex your head forward and feel at the base

of your neck. That posteriorly directed protrusion is the prominent

spinous process of C7. The remainder of the cervical vertebrae are

characterized by bifid (forked) spinous processes and transverse foramina

(for the vertebral artery).

The distinctive features of thoracic vertebrae relate to the joints

formed with the ribs and the direction of their spinous processes. Thoracic

vertebrae are the only vertebrae with impressions (facets or demifacets)

left by the ribs because they are the only vertebra that articulate with

the ribs. Facets or demifacets are found on both the bodies and

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transverse processes of all thoracic vertebrae. Also, their spinous processes

tend to be very "pointy" and directed more inferiorly than those of cervical

or lumbar vertebrae.

Lumbar vertebrae carry most of the weight of the upper torso and

hence are very "heavy" and "chunky" in appearance. Their spinous

processes point directly posterior and are quadralateral or squared off in

shape. Their superior and inferior articular facets are oriented in the

saggital plane unlike those of the cervical (oriented mostly in the

horizontal plane) and thoracic (oriented in the coronal plane) regions.

The orientation of these articular facets and the intervertebral joints

they form with one another largely determine what kinds of movements

are possible at each vertebral level—primarily rotation of the head in the

cervical region, primarily lateral flexion in thoracic region, and primarily

flexion and extension in the saggital plane in the lumbar area. Study the

orientation of the articular facets at cervical, thoracic and lumbar levels of

the vertebral column.

Between each vertebra is an intervertebral disc (see Figure 7.14).

The discs act as shock absorbers between each vertebra and are exposed to

considerable stress, especially in the lumbar region. The disc is composed

of an outer fibrous ring called the annulus fibrous and a soft inner core—

the nucleus pulposus. Sometimes the nucleus pulposus herniates or

ruptures through a weakened portion of the annulus fibrosus. Pain is

usually present and chronic because of the pressure exerted on one or

more spinal nerves. This condition is known as a herniated disc.

The sternum, sometimes called the "breast bone," has three distinct

parts (see Figure 7.19): the manubrium, body and xiphoid process. Note

the jugular notch which you can palpate on your own body where both

your collar bones converge. You can also palpate the costal margin formed

by the costal cartilages of ribs eight–nine. The costal margins of each side

converge medially at the xiphoid process as the costal angle.

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Also pay attention to the number of ribs that articulate with the

sternum. The upper seven ribs that articulate with the sternum via a costal

cartilage are called "true ribs." You should discern why the remaining five

ribs are called "false ribs."

Figure 7.20 displays a typical rib. Take note of the head, tubercle,

and angle of the rib. In life, intercostal nerves, arteries, and veins run in

between the ribs, protected by the costal groove.

Briefly study Figure 7.20 that shows the joint formed between a rib

and a vertebrae. Figure 7.20 shows an especially good view of the

articulation between the vertebral body and transverse process and

the head and tubercle of the rib.

Posture abnormalities can be exaggerations of normal curves or

curves in a plane other that the saggital plane. Kyphosis is an exaggeration

of the thoracic curve, whereas lordosis is an exaggeration of the lumbar

curve. Both, however, present as curves in the saggital plane. In contrast,

scoliosis is a curve in the coronal plane. Hence, it is much more difficult to

correct.

Sample Questions

1. The dens is found on which of the following bones? a. sternum b. rib c. C2 vertebra d. sacrum

2. This condition is an abnormal curvature of the spine in the frontal

plane. a. kyphosis b. scoliosis c. spina bifida d. lordosis

3. Name the bone directly posterior to the nasal bone.

a. ethmoid b. temporal

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c. occipital d. sphenoid

4. Ribs attached directly to the sternum by means of costal cartilage are

referred to by this name. a. floating b. deviated c. false d. true

5. Which of the following bones is paired?

a. frontal b. mandible c. sphenoid d. zygomatic


1. c; 2. b; 3. a; 4. d; 5. d

Go on to Lesson 8.

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Lesson 8 The Appendicular Skeleton

Reading Assignment

Read Chapter 8 in your textbook. As with the chapter on the axial

skeleton, pay close attention to the objectives as you read. Really study the

figures and test yourself on identifying bones and landmarks on the bones.

Pay special attention to the articular surfaces on the bones of the

appendicular skeleton.

Objectives


1. Identify the bones of the shoulder girdle and important landmarks

on the scapula and clavicle (Figures 8.1–8.2)

2. Identify the bones of the upper extremity (including the hand) and

important landmarks (Figures 8.3–8.5; 8.7).

3. Identify bones and landmarks associated with the following joints:

sterno-clavicular, acromio-clavicular, gleno-humeral, elbow

(including proximal radio-ulnar), wrist, metacarpo-phalangeal,

interphalangeal.

4. Identify three bones that comprise the pelvis and key landmarks

(Figure 8.8).

5. Identify bones of the lower extremity (including the foot) and key

landmarks (Figures 8.10–8.12).

6. Identify bones and landmarks associated with the following joints:

hip, knee (hinge and plane), ankle, metatarso-phalangeal.

7. Describe these clinical applications: fractured clavicle, carpal tunnel

syndrome, metatarsal stress syndrome.

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Discussion

As you can see from the list of objectives, this is another one of

those chapters that requires sustained effort and rehearsal. It makes

considerable sense to approach the bones and markings you have to learn

in logical units. It is very important to learn the bones and their markings

well because many of them are involved in the formation of joints, which

you will study later, and/or serve as points of attachment for muscles,

which you will also learn later. Of course, I continue to recommend that

you photocopy your diagrams, clip off the labels and then try to label the

markings yourself.

I recommend that you begin by studying Figures 8.1, 8.2, 8.3, 8.4,

8.5, and 8.7. This may seem like a lot to begin with, but I do not expect you

to learn the entire shoulder girdle and upper extremity the first time

through. I do believe that you will be surprised by how much you do know

after a couple of rehearsals.

One particularly confusing series of terms includes the conoid

tubercle (on the inferior surface of the clavicle), the coracoid process (on

the scapula) and the coronoid fossa (on the anterior, inferior surface of the

humerus). As you can see, the words are very similar in appearance. But, if

you place the markings in alphabetical order and start with the most

medial and superior bone, then work out and down, you will associate

each marking with the right bone: clavicle-conoid tubercule, scapula-

coracoid process, humerus-coronoid fossa.

Another part of the upper extremity that tends to give people

trouble is the wrist. I have no magic solutions for you, but I do have a

couple of tips. First, learn the bones in two rows of four each—a proximal

row and a distal row. Second, learn the bones in the anatomical position,

anterior or palmer side. Third, remember the bones from the thumb side

in because the thumb (pollex) is the prominent digit of the hand (note that

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metacarpals are numbered 1–5, beginning with the metacarpal associated

with the thumb). Also, do not make the common error of thinking that the

scaphoid bone is the carpal bone proximal to the first metacarpal; as you

can see in Figure 8.7, it is not.

As you study the bones and landmarks of the shoulder girdle and

upper extremity, you should begin to appreciate how the landmarks on

different bones fit together to form the joints that you will study in the

next lesson. The shoulder girdle actually is comprised of three separate

joints between the sternum, clavicle, scapula, and humerus.

The clavicular notch of the manubrium receives the sternal

extremity of the clavicle to form the sterno-clavicular joint. The acromion

of the scapula articulates with the acromial extremity of the clavicle to

form the acromio-clavicular joint (see Figure 8.1a). The glenoid cavity of

the scapula and the head of the humerus form the gleno-humeral joint (see

Figure 8.1a). The latter is the joint that people commonly refer to as the

"shoulder joint," but as you can see, the shoulder is really more than the

gleno-humeral joint alone.

When an individual sustains a "separated shoulder," he has

damaged the acromio-clavicular joint. This is different than a "dislocated

shoulder," which refers to a dis-articulation between the head of the

humerus and the glenoid cavity of the scapula.

Likewise, the elbow joint is comprised of more than one joint. The

articulation between the capitulum of the humerus and the head of the

radius, and the articulation between the trochlea of the humerus and the

trochlear notch of the ulna collectively form the joint we normally call the

elbow joint (see Figure 8.5). But there is another articulation at the elbow

that allows for pronation and supination The articulation between the

head of the radius and the radial notch of the ulna (see Figure 8.5) is

known as the proximal radio-ulnar joint.

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Distally, the radius forms the wrist joint with two of the carpal

bones of the proximal row—the scaphoid and the lunate. Notice that the

ulna is not involved in the formation of the wrist joint.

Finally, joints are formed between the distal end of the metacarpals

(head) and the bases of the associated proximal phalanges—the

metacarpal-phalangeal joints. Interphalangeal joints are formed between

adjacent phalanges (heads articulate with bases). Collectively, the joints of

the hand provide for fine motor movements and allow the human species

considerable precision in the manipulation of tools, appliances, and even

sport devices (e.g., baseballs).

Take the same approach to learning the bones of the pelvic girdle

and lower extremity. Start by rehearsing the bones and markings in

Figures 8.8, 8.10, 8.11, and 8.12 a few times. Then, test yourself over the

material. Again, I believe you will be astounded at the amount of

information you have learned after only a time or two through the

information.

In the pelvic girdle, you have quite a challenge. The pelvic girdle

(Figure 8.8) is composed of three distinct bones that fuse in the

acetabulum. The ilium, ischium, and pubis each contribute about one-

third to the acetabulum. The ilium is the superior bone; the ischium is the

posterio-inferior bone; and the pubis is the anterior-inferior bone. I think

the key to learning the markings on all three bones is keeping yourself

oriented; knowing whether you are looking at the medial or lateral surface

of the pelvic girdle. It seems logical to pick out one key landmark to orient

yourself with. Before I tell you mine, why don't you pick one that makes

sense to you? So long as you are comfortable with the landmark you

picked, there is no reason to adopt mine. But if you like, you are certainly

welcome to use mine—maybe you picked the same one anyway. I like to

use the acetabulum because if I can see it I know I am looking at the lateral

surface of the pelvic girdle. If not, then I must be viewing the medial

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surface. It makes a lot of sense to use the acetabulum to me because I

know the head of the femur must fit into a laterally placed socket in order

to work properly.

Actually, I think you will find the lower extremity a little easier;

there are somewhat fewer bones and fewer markings than with the upper

extremity.

Notice that there are several parallels between the ankle (tarsals)

and the wrist (carpals), and between the phalanges of the hand and the

foot. But don't get over-confident; there is one less tarsal than carpal, and

the metatarsals are numbered from medial to lateral (starting with the big

toe—the hallux), just the opposite of the metacarpals. (This is because the

numbering always begins on the side of the great digit. The thumb is

lateral in the anatomical position, while the great toe is medial in the

anatomical position.)

Again, take breaks in learning the material by answering the health

and clinical application objectives.

As you did while studying the bones of the upper extremity and

shoulder girdle, so too you should take note of the landmarks on bones

that enter into articulations. The pelvic girdle is simpler than the shoulder

insofar as the three bones of the pelvis are fused in the acetabulum and the

only other bone involved is the femur.

The three bones of the pelvis (Figure 8.8); the ilium, ischium, and

pubis, fuse to form the acetabulum. In turn, the acetabulum receives the

head of the femur (Figure 8.10) to form the hip joint. Curiously, a

fractured hip that often results from a fall, especially in older adults, is not

a fracture to the bony pelvis at all. Actually, the neck of the femur is most

often fractured as a result of the trauma associated with the fall, or as a

result of osteoporosis or, more likely, a combination of the two.

The knee joint is formed from three bones (Figure 8.10 and 8.11):

the condyles of the femur, the condyles of the tibia, and the facets on the

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posterior surface of the patella. The flexion and extension at the knee are

accomplished as a result of the articulations between femoral and tibial

condyles. The patella slides superiorly and inferiorly on the femoral

condyles as the knee is flexed and extended (a plane joint). The patella acts

as a pulley for the quadriceps femoris muscle group that produces

extension of the leg (as in kicking a football). The movement of the patella

constantly adjusts the angle of the pull of the quadraceps femoris to

maximize its power. Note that the fibula is not part of the knee joint.

However, the lateral malleolus (Figure 8.11) of the fibula helps form

the ankle joint along with the medial malleolus of the tibia (Figure 8.11)

and the talus (Figure 8.12) of the tarsals. The distal ends of the tibia and

the fibula are held together with a strong ligament to provide stability

between the two bones during weight-bearing and ambulation.

Finally, joints between the metatarsals and proximal phalanges

(Figure 8.12) and between adjacent phalanges are identical to those of the

hand. Hence, the joint of the foot confer considerable mobility to

movements of the toes, even though most of us do not appreciate this

capability.

Note the clinical applications for a fractured clavicle, carpal tunnel

syndrome, and metatarsal stress syndrome. Each clinical application is

explained by short sections distributed throughout Chapter 8.

Sample Questions

1. How many phalanges, carpals, and metacarpals are there in one hand? a. 31 b. 27 c. 22 d. 19

2. A hip fracture is actually a break in this bone.

a. ilium b. ischium c. pubis

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d. fermur

3. On which bone are the glenoid cavity and the acromion found? a. humerus b. tibia c. clavicle d. scapula

4. Name the medial bone of the leg.

a. tibia b. fibula c. calcaneous d. navicular

5. What is the name given to the distal articular surface on the femur?

a. condyle b. intertrochanteric crest c. linea aspera d. favea capitis


1. b; 2. d; 3. d; 4. a; 5. a

Go on to Lesson 9.

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Lesson 9 Joints

Reading Assignment

Read Chapter 9 in your textbook. Work through the reading

materials slowly, again paying considerable attention to the figures.

Objectives


1. Define an articulation and identify factors that limit movement at a

joint.

2. Classify joints by structure and function (Table 9.1 and Figures 9.1–

9.3).

3. Recognize characteristic synovial joint features and frequent

accessory structures: (Figure 9.3).

4. Identify movements possible at synovial joints (Table 9.3, 9.4 and

Figures 9.5, 9.6).

5. Identify the six classes/shapes of synovial joints (Figure 9.7).

6. Compare movements permitted according to the various subtypes

of synovial joints (see assignment at the end of this lesson).

7. Identify skeletal components, movements, joint shapes, ligaments,

and cartilagenous structures at the following selected joints:

Shoulder (gleno-humeral) (Figure 9.8), Elbow (Figure 9.9), Hip

(Figure 9.11), Knee (Figure 9.12), Ankle (Figure 9.15).

8. Define the following clinical applications: sprains, dislocations,

subluxations, arthritis (rheumatoid, osteo, gouty), Lyme disease,

and ankylosing spondylitis.

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Discussion

There is some preliminary work to do that pertains to the first few

objectives; then you can start to study specific joints. To begin with, a joint

is a location where one bone meets another bone or cartilage.

Joints are classified in two ways: by function and by structure.

Functional classification of joints is based on the amount of movement

allowed: immovable (synarthrodial), slightly movable (amphiarthrodial),

and freely movable (diarthrodial).

The structural classification of joints basically looks at how the joint

is held together. If the joint is bound by fibrous connective tissue

(remember the strength of collagen fibers), then it is a fibrous joint

(suture, syndesnosis).

Cartilaginous joints are bound together by (you guessed it!)

cartilage. There are two types of cartilagenous joints. We have actually

considered a synchondrosis already—technically, the epiphyseal plate is

considered a synchondrosis type joint. Costal cartilages also qualify the

articulations between ribs and sternum as a syndhondrosis. Intervertebral

discs qualify as a symphyseal type of cartilaginous joint, the connective

tissue is fibrocartilage.

The more interesting joints for the purposes of sport, exercise, and

human movement are the freely movable joints. This category exclusively

includes synovial joints.

You should study and know the prototypical synovial joint (Figure

9.3) very well. Pay particular attention to the minimal features necessary

for a joint to be classified as a synovial type: joint cavity, articular capsule,

and articular cartilage. As you will find out later, there are additional

structures that you might find in a synovial joint (articular discs,

ligaments, etc.), but those listed above are the minimum number of

structures for a joint to qualify for the synovial category. Synovial joints

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get their name from the synovial membrane that lines the inside of the

joint capsule and secretes the lubricating synovial fluid.

You should next study the types of movements possible at a

synovial joint. I would recommend you use Figures 9.5 and 9.6 and

practice each of the movements. Next, have a friend, spouse, or child test

you by doing each of the movements. Your task would be then to recognize

each of the movements demonstrated.

While you are practicing each of the movements, you might want to

think about those anatomical features that limit movement. There are four

factors that limit movement: muscle strength, tension of ligaments, bone

morphology (shape), and soft tissues. For instance, the shape (structure)

of the trochlear notch of the ulna and the trochlea of the humerus allow for

only one type of angular movement—flexion/extension.

Note some clarifications for movements. In the hand, taking the

fingers away from the mid-line of the hand is abduction; the opposite is

adduction. Technically, circumduction is only possible at ball and socket

joints.

Next, study the different subtypes of synovial joints based on the

shapes of articulating bones. As you can see in Figure 9.7, the shapes

(structure) of articulating bones largely determine the kind of

movement(s) allowed at a synovial joint. Also, once you believe you have

learned synovial joint types fairly well, try to determine the kinds of

movements allowed at each. We will reinforce the relationship between the

structure (shape) of synovial joints and movements possible through the

written assignment at the end of this lesson.

Now for the tough part. Work your way through each of the joints

listed in your objectives and study the figures (9.8 through 9.15) that

pertain to each. Try to get a general sense of how the ligaments are placed.

Identify other accessory structures (articular discs, etc.). For example, you

should know that collateral ligaments prevent abduction and adduction in

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the coronal/frontal plane at hinge joints. Hence, collateral ligaments

stabilize joints such as the elbow and the knee.

Don't overlook the articulating bones, the type of joint you are

studying, and the movements possible at each joint listed in the objectives.

Make sure to study the material in Table 9.2 that pertains to each joint.

Take breaks by reading the clinical applications identified in Objective 8.

Remember, do not try to learn everything in one or two nights. Also

remember to test yourself using the copy machine and label method

employed in earlier lessons.

Sample Questions

1. What is the name given to a joint that is united by a dense ligament of fibrous connective tissue? a. gliding joint b. synovial joint c. cartlaginous joint d. fibrous joint

2. What is the clinical term applied to excessive stretching or tearing of

ligaments? a. dislocation b. strain c. sprain d. bursitis

3. This is the special name given to extension of the foot at the ankle joint.

a. hyperextension b. plantar flexion c. dorsiflexion d. abduction

4. Which of the following is not a synovial joint?

a. plane b. hinge c. symphysis d. ball and socket

5. Which ligament below is found at the elbow joint?

a. radial collateral

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b. zona orbicularis c. transverse acetabular d. posterior cruciate


1. d; 2. c; 3. b; 4. c; 5. a


Instructions



Assignments."

Description


1. Compare and contrast knee and elbow joints, noting similarities

and differences between the two. Think about structural and

functional joint type, placement and number of ligaments, number

of bones and articulations in each joint, and movements possible at

each joint.

2. The gleno-humeral joint and the hip joint both qualify as ball and

socket joints. Explain why the gleno-humeral joint seems to be

more mobile then the hip even though both joints are ball and

socket. Explain why the gleno-humeral joint is injured more

frequently.

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Lesson 10 Muscle Tissue

Reading Assignment

Read Chapter 10 and pages 540-542; 649-651 in your textbook. It is

important to really follow your objectives closely because some aspects of

muscle function are not your responsibility. Of course, I still recommend

that you read everything, but spend more time studying the objectives.

Objectives


1. Describe the major characteristics and functions of muscle tissue.

Identify the parts of a muscle (origin, belly, insertion).

2. Define and contrast the three different types of muscle (skeletal,

cardiac, smooth). See Table 10.2.

3. Identify and describe the different connective tissue components in

muscle (Figure 10.1).

4. Define the basic components of a skeletal muscle cell (fiber). (See

Figures 10.4 and 10.6.) Draw a sarcomere. Briefly explain muscle

contraction at the level of the sarcomere (see Figures 10.4 and

10.8).

5. Identify the components of a neuromuscular junction (see Figure

10.9). Define a motor unit and its implications for precise

movements versus gross body movements.

6. Discuss the concept of muscle tone and its implications for posture.

7. Define these clinical applications: muscular dystrophy, muscle

strains, atrophy, hypertrophy, fibromyalgia, and a muscle cramp.

Summarize the detrimental effects of steroid use.

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Discussion

To no one's surprise, muscle tissue is specialized to contract, to

become shorter. In this way, muscles move the bones they are attached to.

However, excitability, extensibility and elasticity, also number among the

characteristics of muscle tissue.

There are three different types of muscles (see Table 10.2) that can

be distinguished on the bases of voluntary versus involuntary control,

striated versus non-striated, location, fiber shape and number of nuclei.

Skeletal muscle is sometimes called voluntary muscle because we have

conscious control over it. But there are many important motor activities

that we do not consciously control. Most of us know that we do not have to

consciously think to make our hearts (cardiac muscle) beat (a good thing,

too, since I'm very forgetful). But involuntary muscle (smooth muscle) also

lines the small intestine and its contractions help us digest food.

Involuntary muscle (smooth muscle) lines the walls of many medium-

sized and small arteries and its contraction (and relaxation) helps regulate

blood flow to certain areas of the body. We will spend most of this lesson

focused on skeletal muscle.

Skeletal muscles move the skeleton and are what most people think

of as muscles. Most skeletal muscles have two attachments (or more)

between bones and the contracting muscle. The muscle is referred to as

the belly or gaster. The attachment that moves is called the insertion; the

stable attachment is the origin.

People are also sometimes surprised to learn that muscle tissue

proper contains connective tissue. The primary connective tissue

components are illustrated in Figure 10.1. Endomysium surrounds each

muscle cell (also called a muscle fiber). Perimysium surrounds a group of

muscle cells, called a fascicle. Finally, epimysium surrounds the entire

muscle. These three layers of connective tissue converge on the

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attachments of muscle to bone and actually become a cord of connective

tissue called a tendon.

The important thing to remember when looking at the structure of a

muscle cell is to understand when you are looking at a cell and when you

are looking at something inside a cell. A muscle fiber and a muscle cell are

one and the same thing, though this can be somewhat confusing. Look for

the endomysium because you know that it surrounds one cell at a time.

Like any other cell, a muscle fiber (see Figure 10.4 and 10.6) is

covered by a cell membrane, known as a sarcolemma. However, muscle

cells are usually studied in smaller functional units. These functional units,

called sarcomeres, can be thought of in the same way as any other

intracellular organelle. (Precisely speaking, sarcomeres are not organelles.

But it makes sense to think about them as organelles because then you

know you are looking at something inside a cell and not looking at the

outside of a cell.) A sarcomere is pictured in Figure 10.4d. Sarcomeres are

defined as running from Z line to Z line and contain the contractile

proteins (myofilaments) that result in the shortening of the muscle proper

and the production of movement. There are thick myofilaments (myosin)

and thin myofilaments (actin), which you can see in Figure 10.4. Together,

the Z lines, thick myofilaments and thin myofilaments, overlap

intermittently to form three areas or bands. There is an I band, and an A

band and an H zone. In a relaxed state the following are true (see Figure

10.7):

a. I bands contain thin myofilaments only,

b. the A band contains thick and thin myofilaments,

c. and the H zone contains only thick myofilaments.

The sliding filament theory of contraction (see Figures 10.7 and

10.8) hypothesizes that proteins within the thick and thin myofilaments

articulate to form "cross-bridges" with one another and pull the Z lines of

the sarcomere closer together. Said another way, the thin myofilaments of

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a sarcomere move inward, toward one another during contraction.

Multiplied many times in many sarcomeres through a muscle, the result is

observable contraction (shortening) of the muscle and movement. Now

study Figures 10.7 and 10.8 and deduce what happens to the A and I bands

and H zone after contraction.

A neuromuscular junction is crucial to muscle contraction. It

represents the meeting place of nerve and muscle tissues, the place where

the nervous impulse (command to contract) is actually given to the muscle

as a chemical message. Figure 10.9 shows the structure of a

neuromuscular junction. Note the components of the neuromuscular

junction. The chemical message or command is contained within synaptic

vesicles in the nerve fiber. When a nervous impulse reaches the end of the

nerve fiber, it causes the vesicles to release their chemical message in the

form of a neurotransmitter. The neurotransmitter then crosses the

synaptic cleft to bind with the sarcolemma (muscle cell membrane) to

stimulate the muscle fiber. Neurotransmitters differ depending upon the

tissue type, but the neurotransmitter for skeletal muscle is acetylcholine.

A motor unit consists of a motor neuron (motor nerve cell) and all

of the muscle cells it stimulates. There are gross and fine motor units.

Gross motor units have one neuron innervating many muscle cells (up to

several hundred), whereas fine motor units have far less muscle cells

innervated by a motor neuron (ten and sometimes less). Fine motor units

are found in areas where precise movement is required, such as the hands,

the face, and muscles of speech. Muscles responsible for large or gross

movements, like running or jumping, tend to have gross motor units

(muscles of the back, trunk, thighs, and legs).

Muscle tone (not to be confused with an isometric contraction) is

the state of partial contraction assumed by skeletal muscle. Tone confers

resilience on a skeletal muscle. But the number of muscle fibers in the

muscle that are contracting is not enough to produce observable

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movement. Muscle tone is essential to maintaining good posture because

it usually amounts to holding the position of the body steady while other

parts work (e.g., hands and upper extremities).

Muscle tissue is not often affected by pathology, though it is often

the site of relatively minor injury (strains, cramps). Some disorders of

muscles cause a decrease in muscle size, called atrophy, because of a loss

of contractile units within a muscle fiber. Muscular dystrophy, for

example, is an inherited disorder of muscle tissue which causes a

progressive loss of contractile units in muscle, with replacement by fat and

connective tissue. However, pathology is not the only cause of atrophy in

the muscle system; simple disuse, lack of exercise, will also result in

atrophy.

Unlike muscular dystrophy, myasthenia gravis affects the neuro

muscular junction. Anti-bodies produced by the individual block

transmission of a nerve impulse at the neuromuscular junction causing

weakness and early fatigue.

Fibromyalgia is sometimes called arthritis of the muscle system. Its

symptoms include pain over numerous "tender points" across the body.

The patient is also plagued by sleep disturbance, often accompanied by

depression.

Unfortunately, social pressure on youth often leads to drug abuse in

an effort to increase the strength of a muscle. Although a muscle will get

larger (hypertrophy) and stronger in response to exercise, use of steroids

(synthesized testosterone-like substances) will cause hypertrophy as well.

Serious physical complications associated with steroid abuse present

significant danger (see page 254).

Sample Questions

1. Name the property that gives muscle tissue the ability to receive and respond to stimuli.

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a. contractility b. excitability c. elasticity d. extensibility

2. Name the stationary attachment of a muscle.

a. tendon b. aponeurosis c. origin d. insertion

3. What is the connective tissue component of skeletal muscle that

surrounds a muscle fascicle? a. perimysium b. epimysium c. endomysium d. tendomysium

4. The term motor unit is applied to this.

a. connective tissue coverings around a muscle b. the union of a muscle's tendon with the periostium of bone c. a motor neuron and the muscle fibers it stimulates d. the triad of a skeletal muscle fiber

5. This portion of a sarcomere contains thick myofilaments only.

a. A band b. I band c. H zone d. Z line


1. b; 2. c; 3. a; 4. c; 5. c

Go on to Lesson 11.

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Lesson 11 Muscle System

Reading Assignment

Read Chapter 11 in your textbook. As with the past few chapters

now, you will find Chapter 11 involves more studying of figures than actual

reading. Also, as before, I strongly urge you to take the time to learn the

objectives very well.

Objectives


1. Define muscle (ms.) actions: agonists (synergists), antagonists,

fixator.

2. Define first, second, and third class levers, noting placement of

fulcrum, resistance, and effort along lever arm. (Figure 11.2)

3. Identify (visually) and know the general attachments and primary

(usually angular) actions for the following ms.:

a. Muscles that move the vertebral column: rectus

abdominis, quadratus lumborum, external abdominal

oblique, internal abdominal oblique, psoas major, iliacus,

erector spinae group (iliocostalis, longissimus, spinalis). See

Figures 11.11 and 11.13.

b. Muscles of the abdominal wall: external abdominal

oblique, internal abdominal oblique, transversus abdominis,

rectus abdominis. See Figure 11.13.

c. Muscles of respiration: diaphragm, external intercostal,

internal intercostal. See Figure 11.12.

d. Muscles that act on the head: Sternocleidomastoid,

semispinalis capitis, splenius capitis, longissimus capitis,

trapezius. See Figure 11.11.

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e. Muscles that act on the pectoral girdle: pectoralis

minor, subclavius, trapezius, levator scapulae, rhomboideus

minor, rhomboideus major, serratus anterior. See Figure

11.15.

f. Muscles that move the humerus: pectoralis major,

latissimus dorsi, deltoid, teres major, supraspinatus, teres

minor, infraspinatus, coracobrachialis, subscapularis. See

Figure 11.16.

g. Muscles that act on the forearm: biceps brachii,

anconeus, brachialis, triceps brachii, brachioradialis,

supinator. See Figure 11.16.

h. Muscles of the forearm that act on the wrist, hand,

and digits: flexor carpi ulnaris, flexor carpi raidalis,

palmaris oongus, flexor digitorum superficialis (superficial

digital flexor), flexor digitorum profundus, flexor pollicis

longus, abductor pollicis longus, extensor pollicis longus,

extensor pollicis brevis, extensor digitorum, extensor carpi

radialis longus, extensor carpi radialis brevis, extensor carpi

ulnaris, pronator teres, pronator quadratus. See Figures 11.17

and 11.18.

i. Intrinsic muscle of the hand: abductor pollicis brevis,

flexor pollicis brevis, opponens pollicis, adductor policis,

lumbricals, palmar interossei, dorsal interossei, abductor

digiti minimi, flexor digiti minimi, opponens digiti minimi.

See Table 11.14 and Figure 11.19.

j. Muscles that move the thigh: psoas major, iliacus,

pectineus, gluteus maximus, gluteus medius, gluteus

minimus, tensor fasciae latae, adductor magnus, adductor

longus, adductor brevis, gracilis, rectus femoris,

"hamstrings," sartorius. See Figures 11.20, 11.21.

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k. Muscles that move the leg: sartorius, quadriceps femoris,

(vastus intermedius, vastus lateralis, rectus femoris, vastus

medialis), "hamstrings" (semimembranosus,

semitendinosus, biceps femoris), gastrocnemius. See Figures

11.20 and 11.21.

l. Muscles that move the ankle, foot, and toes: tibialis

anterior, extensor digitorum longus, extensor hallucis

longus, peroneus tertius, gastrocnemius, soleus, tibialis

posterior, flexor digitorum longus, flexor hallucis longus,

peroneus longus, peroneus brevis. See Figures 11.22, 11.23

and 11.24.

4. Describe most body movements as activities of groups of muscles

by explaining the roles of agonists, and antagonists.

Discussion

You have probably already deduced that the muscular system

should be entitled more specifically "the skeletal muscular system"

because the lesson involves exclusively those muscles that produce

observable and voluntary movement. So any use of the word "muscle" in

this lesson means skeletal muscle.

Analysis of muscle actions involves a set of terms used to describe

what a muscle is doing at a particular time, during a particular movement.

An agonist refers to the muscle(s) doing the work and shortening. The

antagonist is the muscle that must relax in order for the movement to

occur. The antagonist will usually produce the movement that is the exact

opposite of the movement produced by the agonist. As you work your way

through the objectives on specific muscles, try to think in terms of group

actions and the muscles that are agonists and antagonists. Concentrate on

flexion/extension, abduction/adduction and rotation. Muscles that

produce the same action are also said to be synergists.

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Figure 11.2 illustrates the three different types of levers: first,

second and third class. Analogies to a see-saw, wheelbarrow, and lifting an

object with tweezers are provided. Note that the most common type of

lever is the third class. Further note that third class levers are at a

mechanical disadvantage, but are well designed for rapid movement over

an extensive range of motion (as in running or throwing).

I would advise that you tackle the list of muscles you see in

Objective 3 in a logical manner. First, try to identify the major muscles in

Figure 11.7. Most people think it is helpful to study: 1. muscles acting on

the trunk and axial skeleton, 2. muscles of the shoulder girdle and upper

extremity, 3. muscles on the pelvic girdle and lower extremity. After you

can identify the muscles listed in the objectives, then start to study the

appropriate figures and accompanying tables. Try to construct logical

groupings of muscles that perform the same action. This will ease your

load.

Some clarifications:

1. You do not have to know all of the specific muscles of the erector

spinae; just remember it as one muscle with three parts: the lateral

iliocostalis group, the intermediate longissimus group, and the

medial spinalis group.

2. Some muscles are noted several times because they produce actions

at more than one joint (e.g., psoas major). Muscles that act on the

axial skeleton are particularly likely to fall into this category.

The other tip I give you is to make your own muscle flashcards.

True, there are very attractive commercial alternatives and even computer

software that will help you rehearse. But the advantages to making your

own are several. First, I believe you will learn a great deal from the act of

making your own flashcards; you get that extra mental rehearsal when you

construct your own flashcards. Second, it is a lot cheaper to make your

own flashcards. All you need are some index cards. Third, you can pass

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them down to your children when they come of age. (Just kidding on the

last advantage.)

Begin by listing the name of the muscle in the top left corner of the

index card. Then, write down the actions and attachments (origin,

insertion) of the muscle under the name. Leave a little room on the left

margin. This is where I write down the number of actions for the muscle.

Then, when I quiz myself, I can cover over the actions and know that I

must come up with one, two, three or more actions. Remember

attachments in general.

Let us try an example for the biceps brachii muscle. If you look up

the muscle, you will find that it has two primary actions (flexion of the

forearm, and supination), two origins and one insertion. Hence, I would

write the number "2" in the left margin for two actions to remember. For

our purposes, the general attachments to remember are scapula

(origin) to forearm/radius (insertion). You do not need to remember the

specific landmarks for attachments on bones. When it comes time to

study, I cover everything on the card except the name of the muscle and

the number I placed in the left margin. In this case, I know I must name

two actions.

Remember to identify the muscle as well on Figure 11.7. I could

always ask you facts about the muscle's location. For the biceps femoris I

could ask: "Is the muscle located on the posterior surface of the thigh?" "Is

the muscle superficial or deep?" "Is the muscle found in the lower

extremity?" or "Is the biceps femoris seen on a superficial view of the

posterior thigh?"

With regard to actions, think first mostly in terms of angular

motions (flexion/extension and abduction/adduction) or rotation; or

hybrids of angular movements or rotation (dorsiflexion, pronation, etc.).

Hint: You will only find significant rotation at ball-and-socket and pivot

joints. Another hint: The actions of the muscles that move the foot are

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determined by where each muscle's tendon passes the ankle (those of the

anterior compartment dorsiflex; those of the lateral and posterior

compartments plantarflex). Third study hint: Try to get a sense for

whether a muscle is deep, intermediate, or superficial, relative to other

muscles. This exercise will make subsequent identification of muscles

considerably easier. Remember your self-tests; all it takes is a photocopy

and discipline. Final hint: As a general rule of thumb, in the anatomical

position, muscles on the anterior parts of the neck, arms, forearms, chest,

and abdomen are flexors. Muscles on the anterior aspect of the thigh are

extensors (of the knee). Muscles on the posterior aspect of the neck, arms,

forearms, back, and buttocks are extensors. Muscles on the posterior

portion of the thigh are flexors. (Some muscles act on more than one joint:

take special note of these as well.)

Sample Questions

1. Name the muscle from the list below that is antagonistic to plantor flexion of the foot. a. peroneus brevis b. soleus c. tibialis anterior d. flexor hallucis longus

2. What is the name of a muscle that performs the desired action?

a. antagonist b. agonist c. synergist d. fixator

3. What is the primary action of the palmar interossei?

a. adduct digits b. flex digits c. abduct digits d. extend digits

4. This muscle turns the palm upward or anterior.

a. fibialis anterior b. plantaris

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c. adductor longus d. supinator

5. Which muscle below is not innervated by the obturator nerve?

a. sartorius b. adductor longus c. gracilis d. adductor magnus


1. c; 2. b; 3. a; 4. d; 5. a


Instructions



Assignments."

Description


1. Identify muscles that produce flexion at the hip and their

antagonists. Identify muscles that produce abduction at the hip and

their antagonists..

2. Identify the lever type (first, second, or third class) in effect in

flexing the leg at the knee. Next, identify agonists and antagonists

to flexion of the knee.

Examination #2

Examination #2 follows written assignment #4. This will be a one-

hour, supervised examination. No books, notes, or other aids may be

brought to the exam. The examination consists of forty multiple-choice

questions of the same type you have seen in the sections of sample

questions in each lesson. The exam questions are allocated according to

the number of objectives per topic.

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version only).

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UNIT 4 INTEGRATION

Lesson 12 Nervous Tissue

Lesson 13 Central Nervous System

Lesson 14 Peripheral Nervous System


Lesson 15 Autonomic Nervous System


Lesson 16 Special Senses

Lesson 17 Endocrine System

Examination #3

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Lesson 12 Nervous Tissue

Reading Assignment

Read Chapter 12 in your textbook. As this is the beginning of the

second half of the course, I remind you to use the objectives to guide your

reading.

Objectives


1. Define peripheral and central nervous systems. List the functions of

the nervous system. Classify spinal cord, brain, spinal nerves and

cranial nerves into either peripheral or central nervous system.

Define and distinguish somatic afferents, somatic efferents, visceral

afferents and visceral efferents (Figure 12.3).

2. Classify gray matter versus white matter in the CNS and PNS:

nerve, nucleus, ganglion, and tract.

3. State the general functions of supporting cells/neuroglial cells:

astrocyte, ependyma, oligodendrocytes, and microglia. See Figure

12.12.

4. Define and describe the general features of a typical neuron.

Include the following: dendrite, axon, cell body (perikaryon),

neurolemmocyte (Schwann cell), neurolemmal sheath, myelin

neurofibral node (know Figure 12.4). Also, contrast unipolar

(sensory neuron) (Figure 12.10c). and multipolar (motor neuron)

neurons (Figure 12.10a).

5. Define myelin, know the cells responsible for myelination, and state

the functional significance of myelin. See Figures 12.14 and 12.15.

6. Draw and explain a simple reflex arc (Figure 12.17), identifying its

five components.

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7. Define the connective tissue components of a (peripheral) nerve:

epineurium, perineurium, and endoneurium. See Figure 12.16.

8. Generally describe the components of a synapse: presynaptic

neuron, postsynaptic neuron, synaptic cleft, axon terminal, synaptic

vesicles, neurotransmitters (Figure 12.8).

9. Define and describe multiple sclerosis.

Discussion

A vital point about the nervous system that few books bring out is

no matter how you label and divide the nervous system for study, it is a

continuous entity (see Figure 12.2). Everything is connected! Even

though we might be studying the peripheral nervous system at one time,

the spinal cord at another, and the brain at yet another, the student should

not think the spinal cord is somehow separated from or not connected to

peripheral nerves and the brain. So as you work through the material, keep

this idea tucked away in the back of your mind. It will help you get the "big

picture" and formulate a better understanding of how the entire nervous

system works as one functional unit.

For convenience, the nervous system is often divided into the

central nervous system (CNS) and the peripheral nervous system (PNS).

The central nervous system is all nervous tissue found inside of bone—the

vertebral canal of the vertebral column and the inside of the skull or

cranium. The peripheral nervous system (PNS) is nervous tissue found

outside of bone; basically, everything else.

Nerve cells (neurons) are divided into sensory (afferent) and motor

(efferent). The afferent system is responsible for getting sensory

information to the CNS. The efferent system is responsible for getting

nervous impulses from the CNS to effector organs (like muscles, glands,

smooth muscle in the digestive system, etc.) (see Figure 12.3).

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The efferent (motor) system is further divided according to whether

the neuron innervates a voluntary (skeletal) muscle, or innervates an

involuntary (smooth or cardiac) muscle. The former system is referred to

as the somatic motor system; the latter is called the visceral motor system.

Later, specifically in the lesson on the autonomic nervous system, we will

discuss at length the differences between somatic motor and the visceral

(autonomic) motor systems.

Let's look at a more detailed rendering of the afferent and efferent

systems. The following is a functional classification based on the

direction an impulse is transmitted along nerve cell processes. Sensations

are carried toward the CNS for interpretation and can come from two

sources: sensory impulses coming from organs and blood vessels (referred

to generally as viscera) are carried by visceral sensory fibers and sensory

impulses from about everywhere else in the body (soma means "body") are

conducted along somatic sensory fibers. Motor commands are carried

away from the CNS toward effector organs (muscles) and are classified

according to the type of muscle innervated. If the axon leads to a voluntary

(skeletal) muscle, the neuron is a somatic motor. If the fiber leads to an

involuntary (cardiac or smooth) muscle, it is known as a visceral motor.

As you progress through Chapter 12, you will find a great variety of

cell types. Before you identify the parts of a typical neuron, however, you

should be aware of a category of cells found interspersed among nervous

tissue that are not actually nerve cells. The general title given to this

category of cells is neuroglia. Neuroglial cells assist nerve cells but do not

actually conduct nervous impulses. They support and protect nerve cells as

well as form myelin, a sheath of tissue that surrounds most of the length of

a neuron's axon and/or dendrite and increases the conduction velocity of a

nerve cell. Neuroglial cells are illustrated in Figure 12.12.

The second category of cells found in nervous tissue consists of

nerve cells also called neurons. We will use the neuron diagrammed in

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Figure 12.4 as our typical neuron to identify the component parts of a

nerve cell. Neurons can assume different shapes and sizes, but they all

pretty much have the parts labeled in Figure 12.4. Study Figure 12.4 and

identify the parts listed in Objective 4. Note, 12.4 actually shows two cells,

the motor (efferent) neuron and a neurolemmocyte (Schwann cell). As it

so happens, the motor neuron pictured is found in the anterior gray matter

of the spinal cord. The neurolemmocyte (Schwann cell), however, is found

in many places throughout the nervous system. The neurolemmocyte is

one of several types of neuroglia. It happens to produce myelin which

coats the processes (axons or dendrites) of some neurons.

Just a couple of remarks before we move on:

1. Note: the processes that extend into the periphery as axons and

dendrites are as much a part of the nerve cell (neuron) as the cell

body.

2. Note: the cell that lays down myelin along the length of a nerve

fiber (axon or dendrite) leaves spaces or gaps; these are called

neurofibul nodes (Node of Ranvier).

Returning to Figure 12.4 for a moment, axons from this type of

motor neuron actually compose the somatic portion of the efferent/ motor

system.

Now recall the point I made earlier—although the nervous system

and nervous tissue can be segregated to help us study, it is anatomically

continuous. For instance, the cell body and dendrites of the neuron you

see in Figure 12.4 are typically found within the CNS, but its axon is

usually in the PNS. The axon of the motor neuron in 12.4 is actually the

processes of the neuron that innervates muscle cells. (See the discussion

pertaining to a neuromuscular junction in the muscle tissue lesson.)

A special category of neurons are interneurons (association

neurons). These cells are found in between sensory and motor neurons.

They are also contained entirely within the CNS (brain or spinal cord);

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their axons do not lie outside the CNS as those of sensory and motor

neurons. You do not have to know any particular types of association

neurons, but you should know of them and their function in a conceptual

sense. Technically, all of the neurons of the brain are various types of

association neurons.

Commonly, you will read or hear of white matter and gray matter of

the nervous system. White matter and gray matter are additional ways in

which you can talk about certain parts of the nervous system, different

ways of talking about some of the same structures found in the nervous

system.

I have waited until after the explanation of myelin to discuss gray

matter and white matter because the discussion of myelin was a necessary

pre-requisite. In the simplest terms, white matter appears white or light

colored because it contains axons and dendrites that are myelinated. The

lipid material of myelin confers a lighter hue on some nerve tissue we

designate as white matter. Gray matter is darker in coloration because it

does not contain myelinated axons or dendrites.

In summary, white matter contains myelinated axons or dendrites.

Gray matter contains unmyelinated axons and dendrites and cell bodies

of neurons (which are never myelinated). White matter and gray matter

are further designated depending on whether you find it in the PNS or the

CNS.

White matter in the PNS is designated as a "nerve," while in the

CNS it is called a "tract." Importantly, in both cases what you find in the

white matter is the same—myelinated axons and dendrites. Gray matter in

the PNS is called a "ganglion"; in the CNS it is referred to as a "nucleus."

You will find that these terms will be used more often as you

progress through the chapters on the nervous system. Try not to be

intimidated by the jargon. Sometimes we just use more specific

terminology to refer to structures in order to be more precise. But always

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keep in mind, no matter what kind of "matter" we are talking about, no

matter what part of the entire nervous system we are talking about, it all

amounts to either cell bodies, axons (myelinated and unmyelinated), and

dendrites (myelinated and unmyelinated).

Like muscle, nerves have connective tissue for support. Just as we

saw that muscle tissue has connective tissue components, so too, if you

study Figure 12.16, you will find that nerves include connective tissue

components. The prefix actually tells you what structure(s) the connective

tissue surrounds. For instance, just as endomysium surrounds each

individual muscle cell, the endoneurium surrounds each individual nerve

fiber (axon or dendrite) in the nerve. If the analogy holds, the following

should also be true:

1. perineurium surrounds a group (called fascicle) of nerve fibers in a

nerve,

2. and epineurium surrounds the entire nerve.

Study Figure 12.16 and decide for yourself whether this is the case

or not.

In studying Figure 12.8, much of the terminology should seem

pretty familiar to you. Can you remember where you have seen these

structures before? If you remembered the neuromuscular junction we

studied in the muscle tissue lesson, then terms like axon terminal, synaptic

vesicles, synaptic cleft, and neurotransmitters should be recalled. The

major difference between a synapse and neuromuscular junction is that

the synapse is between two neurons, whereas the neuromuscular junction

is between a nerve cell and a muscle cell. Neurotransmitter receptors on

the postsynaptic membrane receive the neurotransmitter substances after

they have crossed the synaptic cleft. These are not unique to the synapse;

neurotransmitter receptors are also present on the postsynaptic

membrane of the neuromuscular junction.

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Synapses work in only one direction. The presynaptic and

postsynaptic membranes are always the same at any given synapse. Hence,

nervous impulses can travel in only one direction. You do not have to

know specific transmitter substances.

Although "thinking" as we customarily know it occurs only in the

brain, the spinal cord can do a few things on its own. These tasks are called

reflexes because they happen automatically. Take note of the five

components of a reflex arc and Figure 12.17.

For example, imagine that you prick a finger with a pin. The pain

receptor senses "pain," then the impulse is transmitted along a sensory

neuron to an interneuron in the spinal cord. The final part of the arc

consists of the motor neuron sending an impulse to the effector (in this

case a skeletal muscle) to remove your finger from the pin. Get the

"point"? (A little anatomy humor.) This happens automatically, without

conscious thought, and is totally controlled by the spinal cord. Hence, we

call it a spinal reflex.

Multiple sclerosis is a neurological disorder in which the myelin

sheaths surrounding nerve fibers in the CNS deteriorate. It is thought to be

an autoimmune disorder and is more common in temperate climates. The

disorder progresses at different rates in different individuals. Sometimes

initial symptoms subside and the person will be asymptomatic from then

on. More commonly, the disorder progressively worsens with each "attack"

(exacerbation), causing progressively more impairment. Typical symptoms

include blurred vision, slurred speech, muscle weakness/fatigue, balance

difficulties, incontinence, and depression.

Sample Questions

1. This name is given to a neuron that transmits a nerve impulse to the CNS. a. motor b. sensory

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c. bipolar d. interneuron

2. Which cell does not belong with the others because of its function?

a. sensory neuron b. Schwann cell c. motor neuron d. interneuron

3. This portion of the nervous system is usually considered to be

involuntary. a. central b. somatic c. visceral d. peripheral

4. These nerve fibers convey impulses to skeletal muscles.

a. somatic motor b. visceral sensory c. somatic sensory d. visceral motor

5. Name the junction between two neurons.

a. neuromuscular junction b. motor end plate c. hillock d. synapse


1. b; 2. b; 3. c; 4. a; 5. d

Go on to Lesson 13.

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Lesson 13 Central Nervous System

Reading Assignment

Read Chapter 13 and answer the objectives listed below. As before,

pay closer attention to the material associated with the objectives.

Objectives

1. Identify ventricles, interventricular foramina, cerebral aqueduct,

arachnoid villi, choroid plexus, median aperture, lateral aperture.

Explain the formation of cerebrospinal fluid. Define the different

layers of the meninges: dura mater, arachnoid, and pia mater. See

Figures 13.4b, 13.11, 13.30, and 13.32.

2. Identify the gross features of the cerebrum: hemispheres, corpus

callosum, central sulcus, lateral sulcus, longitudinal fissure,

transverse fissure, cerebral cortex, gyri, and sulci (Figures 13.20).

3. Identify the lobes of the cerebrum and the general functions of each

(Figure 13.23).

4. Describe the three types of white matter in the cerebrum and the

general connections established by each: association fibers,

commissural fibers (corpus callosum), and projection fibers

(internal capsule) (Figure 13.26).

5. Identify the components of the basal ganglia/nuclei and its general

function (Figures 13.21 and 13.27).

6. Discuss the significance of cerebral dominance for language. Also

state implications of damage to the areas involved in language

(Auditory association area, Broca's [motor speech] area, arcuate

fasciculus).

7. Identify the thalamus and state its functions (Figures 13.16, 13.17

and 3.18).

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8. Identify the hypothalamus and state its general functions (Figures

13.16 and 13.19). Also, identify the pituitary gland and

infundibulum (pituitary stalk).

9. Identify the main components of the brainstem and connections

with the cerebellum. Specifically, for the midbrain, state the

functions of the superior colliculi, inferior colliculi, red nucleus,

cerebral peduncle, and substantia nigra. In the pons, state the

functions of the pneumotaxic area, apneustic area, and pontine

nuclei. For the medulla, state the functions of cardiac, vasomotor,

respiratory centers, and the "pyramids." See Figures 13.13 and

13.14.

10. Define the reticular formation in the brainstem and state its

functions (Figure 13.29).

11. Identify the anatomy and the functions of the cerebellum, defining

the components of the cerebellar peduncles (Figure 13.15).

12. Describe the gross features and extent of the spinal cord: cervical

and lumbar enlargements, conus medullaris, filum terminale, and

cauda equina (Figure 13.2).

13. Describe and draw a cross section of the spinal cord identifying:

central canal, white matter, gray matter, anterior, posterior and

lateral horns, anterior, posterior and lateral funiculi, gray

commissure, anterior median fissure, and posterior median sulcus

(Figure 13.4 and 13.5).

14. Know general function and location of sensory and motor tracts in

the spinal cord (see Tables 13.6, 13.7, Figure 13.34).

15. Know these clinical applications: effects of spinal cord section at the

level of the cervical enlargement and between cervical and lumbar

enlargements; stroke.

16. Locate the limbic system and define its functions (13.28).

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Discussion

Read Chapter 13 to get oriented. You should know that the brain is

comprised of four parts: the cerebrum, brain stem, diencephalon, and

cerebellum. The entire central nervous system (CNS) is protected by the

meninges.

Three layers of meninges cover and protect the entire CNS. They are

comprised of: an outer tough layer—dura mater; a middle layer—

arachnoid; and an inner, delicate membrane that adheres directly to the

spinal cord and brain—pia mater. The subarachnoid space contains the

cerebral spinal fluid (CSF). This fluid helps protect the spinal cord by

providing a fluid shock absorber to dissipate external blows to the

vertebral column. You can see all of these meningeal structures in Figures

13.4b, 13.11, 13.30 and 13.32.

You should also recognize the dura mater, arachnoid, and pia mater

also cover the brain. These coverings continue throughout the CNS. Figure

13.11 identifies ventricles that are part of the cerebrospinal fluid (CSF)

circulation system. CSF is produced by capillary networks called choroid

plexuses, located in each of the four major ventricles (two lateral, a third

and a fourth).

Three apertures (one median, two lateral) in the fourth ventricle

give CSF access to the subarachnoid space. The CSF moves from the

ventricles into the subarachnoid space and then is returned to the venous

system by dural sinuses (see Figure 13.30). A dural sinus is a venous

channel running through the dura mater. Notice in Figure 13.30a that the

superiorly-directed projections push through the sinus as arachnoid villi

(villus is singular). The arachnoid villi are responsible for returning the

CSF back into the bloodstream. Therefore, CSF circulation begins in the

choroid plexuses of each ventricle where CSF is produced. The CSF finds

its way into the subarachnoid space via one of the three apertures (Figure

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13.11). After a time, the CSF is returned to the bloodstream by way of one

of the arachnoid villi associated with the superior saggital sinus (Figure

13.30).

The cerebrum is the part of the brain most people think about or

picture when the word brain is used. Like the rest of the CNS, the

cerebrum is comprised of gray matter and white matter, except it is

arranged in a fashion just the reverse of that in the spinal cord. The gray

matter (cell bodies mostly) is situated on the outside of the cerebrum; this

area is referred to as the cortex (see Figure 13.23). Study the cerebrum in

Figure 13.20 to identify the structures listed in Objective two.

The white matter (primarily myelinated axons) of the cerebrum is

underneath (deep to) the cortex. It contains three kinds of fibers (axons).

Association fibers connect different lobes on the same hemisphere.

Projection fibers include those axons from the thalamus (by way of the

internal capsule) on their way to the cortex. Projection fibers also include

fibers (axons) from cell bodies in the cortex on their way to the internal

capsule. Some of the projection fibers directed inferiorly eventually

become some of the descending tracts (the corticospinal tracts for

instance). The last type of fiber in the white matter of the cerebrum is

called a commissural fiber. Commissures connect the two hemispheres of

the cerebrum. Study Figure 13.26 to get a sense of what areas the axons of

the white matter of the cerebrum connect. There are anterior and posterior

commissures as well as the largest commissure—corpus callosum. Corpus

callosum is labeled in Figure 13.26.

Figure 13.23 displays a functional map of the cerebral cortex. Be

able to define the general functions of each lobe of the cerebrum. To make

your task a little easier, note that motor areas are confined to the frontal

lobe, whereas sensory areas are found on temporal, parietal, and occipital

lobes. Below is a matching exercise to test your recall after you have

studied the cortical areas of the cerebrum for a while.

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Identify one correct answer for each question.

a. frontal lobe b. temporal lobe c. occipital lobe d. parietal lobe

1. Receives sensory impulses from the eyes and interprets shape and color. 2. This area of the brain receives sensory information from cutaneous,

muscular, and visceral receptors from various parts of the body. 3. Controls voluntary movements of the eye. 4. Controls muscles of speech by translating thoughts into speech. 5. Voluntary control of skeletal muscle, usually on the opposite side of the

body.

Read on for the answers.

The basal nuclei represent a loose coalition of separate nuclei

controlling gross subconscious movements and muscle tone. Swinging of

the arms while walking and contraction of proximal limb musculature in

fundamental movement patterns (e.g., walking, throwing, etc.) are

controlled by the basal nuclei. The basal nuclei are also responsible for

starting and stopping movements. Some instructors liken the basal nuclei

to a "filtering" system because the characteristic sign of dysfunction of the

basal nuclei is involuntary (unwanted) movement (dyskinesia)—as in

Parkinson's disease. If the filter was working, the involuntary movements

would not sneak through.

Identify the parts of the basal ganglia/nuclei (caudate, lentiform

nuclei claustrum) in Figures 13.21 and 13.27. With the substantia nigra

(not pictured), these are major structures in the basal nuclei. (The answers

to the matching exercise are 1. c, 2. d, 3. a, 4. a, and 5. a.)

Proficiency with language, such as understanding the written and

spoken word and speech, are controlled by the so-called dominant cerebral

hemisphere. For most people, the dominant cerebral hemisphere is the

left. (Since cerebral control of the body is contralateral, the dominant

hemisphere usually is associated with the dominant or preferred hand).

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The auditory association area (see Figure 13.23) on the temporal lobe

receives and interprets auditory information (speech comprehension).

Association fibers (the arcuate fasciculus) connect the auditory association

area with the Broca's (motor speech) area on the frontal lobe. This allows

us to hear a question in class, and verbalize an answer to the question.

Damage to any of these structures will result in aphasia (difficulty

using and/or understanding written or spoken language). Note that

aphasia results only when there is damage to one of these areas on the

dominant cerebral hemisphere. This makes language unique because

most other cerebral functions are bi-lateral.

The thalamus is an aggregation of gray matter (nuclei) at the end of

the brainstem; the thalamus is the "gateway" to the cerebral cortex (see

Figures 13.16 and 13.18). Ascending (sensory) tracts travel superiorly

through the spinal cord, then continue on through the brainstem. Hence,

the thalamus relays most types of sensory information (except smell) to

the cerebral cortex via a thick band of fibers (axons), called the internal

capsule (see Figure 13.17b), from the thalamic nuclei.

Below the thalamus (see Figures 13.16 and 13.19) one finds a second

group of nuclei, called the hypothalamus. "Hypo" ("less than" or "under")

suggests the location of these nuclei, directly under the thalamus. The

hypothalamus has several major functions you should remember. It plays

a role in the autonomic nervous system as its major control center. The

hypothalamus also influences the endocrine system through its

communication with the pituitary gland via the infundibulum (pituitary

stalk), illustrated in Figures 13.16 and 13.19 (which we will study more in

the endocrine lesson). There are certain cyclical centers for hunger, thirst,

and sleep patterns. Body temperature is also regulated by hypothalamic

nuclei.

Together the hypothalamus and thalamus are called the

diencephalon.

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The continuation of the spinal cord upward is the brainstem (see

Figures 13.13 and 13.14). The brainstem lies on the ventral or basal surface

of the brain.

All of the parts of the brainstem share several major functions:

1. They act as a conduit for the ascending or descending tracts (in

other words, the brainstem connects the spinal cord to the rest of

the brain and parts of the brain with one another).

2. They house many of the cranial nerve nuclei.

3. They are the home for several other important nuclei, including the

reticular formation (discussed at some length below).

You should know that the brainstem is composed of three parts:

medulla, pons, and midbrain. Each has a connection with the cerebellum.

(Identify the cerebellum in Figure 13.15.). The connections are called

peduncles. The medulla, pons, and midbrain connect with the cerebellum

via inferior, middle, and superior cerebellar peduncles, respectively

(Figure 13.13c).

You should also know the following about each part of the

brainstem:

1. The medulla contains many important "centers" (Figure 13.14) for

vital functions (cardiac rhythm, respiratory rhythm, and blood

pressure). This is why damage to the medulla is often fatal. The

medulla also contains nuclei for cranial nerves 8, 9, 10, 11, and 12.

(Number 8 is shared with the pons.) The medulla is connected with

the cerebellum by the inferior cerebellar peduncle. See Figure

13.13c. The pyramids of the medulla carry motor fibers that

originate in the frontal lobe of the cerebrum, destined for the spinal

cord.

2. The pons also contains several cranial nerve nuclei and pontine

nuclei. The latter send axons to the cerebellum via the middle

cerebellar peduncle. See Figure 13.14. The pons contains nuclei for

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cranial nerves 5, 6, 7, and 8. The pons also helps regulate

respiration through apneustic and pneumotaxic centers.

3. The midbrain, likewise, contains nuclei for cranial nerves as well as

the red nucleus, substantia nigra, and corpora quadrigemina. The

red nucleus is the origin of the rubrospinal tract. The nuclei of the

superior and inferior colliculi serve as the origins for fibers that will

eventually become the tectospinal tract. The substantia nigra joins

several other widely separated nuclei to form a functional unit

called the basal nuclei. The midbrain also houses nuclei for the

third and fourth cranial nerves. See Figure 13.14.

Throughout the brainstem is another poorly organized collection of

nuclei called the reticular formation (see Figure 13.29). The reticular

formation is vital to our general level of alertness and attention. This is

why the reticular formation is sometimes called the reticular activating

system. The reticular formation also plays a role in controlling muscle tone

through its several reticulospinal tracts.

As you can probably tell by now, the cerebrum does not work alone.

We have already identified other parts of the brain, the thalamus and basal

ganglia especially, that play major roles in coordinating things. We need to

add the cerebellum to that list now.

Identify the cerebellum in Figure 13.15. Histologically, the

cerebellum is arranged in a fashion similar to the cerebrum, with cell

bodies (gray matter) on the outside and fibers (white matter) on the

inside. We already noted the cerebellum has three attachments

(peduncles), one with each part of the brainstem (see Figure 13.13c).

Through some of these peduncles, the cerebellum can send axons to

influence and help other parts of the brain do their jobs better.

The cerebellum is primarily a motor coordination center. This

means the cerebellum checks movements as they occur, to assure they are

carried off as planned, so the entire movement appears as one smooth

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whole. If a movement "error" is detected, then the cerebellum alerts other

parts of the brain, so the movement can be corrected. When things go

wrong with the cerebellum, you will sometimes observe a decomposition

of movements, movements which begin to appear short, choppy, and

uncoordinated—a conditions known as ataxia (uncoordinated movement).

The cerebellum is also concerned with control of postural muscles

and equilibrium. Along with its coordination functions, the cerebellum

does all of these tasks at the subconscious level. This is very useful because

it frees up attention and cerebral capacity to think about things far more

interesting than contracting the right muscles so that we can stand or sit

erect. The cerebellum makes life a lot more interesting because it takes

care of almost all of the tedious "work" without having to occupy a lot of

our conscious attention.

You should have a general familiarity with the components of each

of the three peduncles that connect the cerebellum to each part of the

brainstem. The inferior peduncle carries proprioceptive (joint sense)

sensation to the cerebellum. The middle peduncle carries fibers from the

pons to the cerebellum. The superior peduncle carries fibers to the red

nucleus from the cerebellum.

The spinal cord is primarily a pathway for nervous impulses to and

from the brain. It also performs a few simple, protective functions (called

spinal reflexes) on its own. Nevertheless, you should remember that

neurons in the spinal cord are largely under the control of neurons

residing in the brain. This is why some neurons in the spinal cord are

referred to as lower motor neurons (and those in the brain as upper motor

neurons).

Recall that the spinal cord and the remainder of the CNS is

comprised of white matter and gray matter. The gray matter marks the

location of nerve cell bodies and appears as a darker hue because the cell

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bodies of neurons are not myelinated. White matter is made up of

myelinated nerve cell processes—axons and dendrites.

The general features of the spinal cord are illustrated in Figure 13.2.

The spinal cord begins at the foramen magnum (of the occipital bone) and

ends at the level of upper lumbar vertebrae in a tapered structure called

conus medullaris. Inspect the length of the spinal cord proper and note

that it is not of uniform thickness throughout its entire length. Two areas

in particular are wider; they are called the cervical and lumbar

enlargements. What do you think accounts for these enlargements?

Filum terminale arises from the conus medullaris and anchors to

the coccyx. The filum terminale is not nervous tissue. It is, more or less, a

ligament that helps to secure and stabilize the spinal cord in the vertebral

canal. Filum terminale is found in amongst a series of fibers called cauda

equina.

Cauda equina is comprised of nervous tissue. Because the spinal

cord does not extend the entire length of the vertebral column, some nerve

fibers—those in the lumbar, sacral, and coccygeal regions specifically—

must travel inferiorly for a distance to exit at the appropriate vertebral

level. For example, the S1 spinal nerve will exit at the S1 vertebral level,

even though the spinal cord proper ends at about L2. To do this, S1 fibers

must travel downward until they arrive at the appropriate vertebral level.

This effect for lumbar and sacral spinal nerves results in the cauda equina.

Figures 13.4 and 13.5 shows the spinal cord in cross section. The

gray matter, where all the cell bodies are, forms an H-shaped

configuration in the center of the cord. Around the gray matter is white

matter, composed largely of myelinated axons. A gray commissure forms

the horizontal bar of the H in the gray matter. The H-shaped pattern is

also further subdivided into horns, two anterior, two posterior. The white

matter is likewise subdivided into anterior, lateral and posterior funiculi.

The word "funiculus" is used because the white matter contains bundles of

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myelinated axons carrying information up to or down from the brain. Soon

you will learn that each of the funiculi is further subdivided into ascending

or descending tracts. The ascending tracts are carrying sensory

information to the brain; the descending tracts are carrying motor

information to the spinal cord. (It is a good idea to test yourself on Figure

13.5; remember, part of the objective is to draw a cross section of the

spinal cord, too.)

The cell bodies of motor neurons are located in the anterior gray

horn of the spinal cord. The cell bodies of sensory neurons are located in

structures called a dorsal root ganglia—as a cluster of cell bodies in the

PNS. See Figure 13.5.

Just as nerves are white matter in the PNS, tracts are the white

matter in the CNS. Tracts, as we saw before, were defined as columns or

bundles of axons traveling up (ascending tracts) or down (descending

tracts) the spinal cord, to or from the brain. As it so happens, the

organization of tracts is not haphazard, but rather systematic. Axons

carrying similar kinds of impulses (or information) tend to group together

so that we may identify specific tracts carrying specific kinds of

information (sensory or motor). Study Tables 13.6 and 13.7 and Figure

13.34. You should know all sensory (ascending) tracts and motor

(descending) tracts, where they are located in the spinal white matter, and,

generally, what kind of functions they perform. You do not have to know

the reticulospinal tracts.

Many of the tracts are named for where they begin and end, so this

should make your task easier. For instance, the lateral spino-thalmic tract

is located in the lateral white matter of the spinal cord and carries

information from the spinal cord ("spino") to the thalamus ("thalamic") in

the brain. Even if you could not remember that it is an ascending tract, you

could deduce that it is an ascending tract from the name. Likewise,

spinocerebellar tracts go to the cerebellum from the spinal cord. And

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corticospinal tracts go from the cerebral cortex to the spinal cord (anterior

and lateral give locations of the corticospinal tracts in the white matter). It

might be a good idea to test yourself on the function of each tract by

developing a matching exercise. Put the tracts on one side and the

functions on the other, then try and match them up.

Injuries to the CNS are very serious and, too often, permanent.

Trauma to the spinal cord is usually from an external event—such as a

vehicular accident. Although, many different types of injuries may result.

Two of the most common result in paraplegia and quadriplegia. Severing

the spinal cord between cervical and lumbar enlargements denies

voluntary control to both lower extremities. Severing the spinal cord at the

cervical enlargement means that all four extremities are involved—

quadriplegia.

A cerebral vascular accident (CVA) or stroke is a form of brain

injury, making it similar in some respects to any brain trauma except for

etiology. The majority of strokes cause injury by depriving brain tissue of

blood supply (ischemia). In contrast, brain trauma may result from direct

injury to brain tissue, or more commonly, put pressure on brain tissue as a

result of a blood clot (hematoma) associated with damage to meningeal

blood vessels.

In either case, the symptoms are correlated with the extent of injury

and the nature of the damaged tissue. For example, CVAs that affect the

internal capsule (projection fibers) on one side often result in partial or

complete paralysis on the opposite side of the body (contralateral

hemiphagia). Furthermore, strokes to the dominant hemisphere

frequently result in difficulty using or understanding language (aphasia).

Cerebral palsy results when some event causes the fetal brain to be

deprived of an adequate oxygen supply before birth. Hence, cerebral palsy

is a congenital brain injury (in contrast to strokes and traumatic brain

injuries which are acquired). Cerebral palsy most commonly affects motor

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areas of the cerebral cortex, but may affect the basal nuclei or the

cerebellum. Symptoms manifest as syndromes of motor impairments,

such as spasticity of control, disruption of muscle tone and function,

ataxia, and other motor dysfunction

The limbic system is illustrated in Figure 13.28. It is generally

regarded as the primitive brain and comprised of nuclei that surround the

brainstem—primarily the amygdaloid nucleus, fornix, hippocampus, and

cingulate gyrus. The limbic system is primarily involved in primitive

emotions and, surprisingly, memory. Several structures in the limbic

system are subject to considerable research effort because deterioration of

some of the nuclei is associated with one type of senility/dementia

(Alzheimer's disease). Note also the involvement of the olfactory nerve in

the limbic system—a basis for the ability of perfume and after-shave to

provoke sex-drive.

Sample Questions

1. This structure serves as a relay for sensory information bound for the cerebral cortex. a. cerebellum b. thalamus c. midbrain d. basal ganglia

2. An obstruction in an interventricular foramen would interfere with

flow of CSF into this space. a. lateral ventricle b. third ventricle c. fourth ventricle d. median aperture

3. This lobe of the brain is responsible for controlling voluntary motor

activity. a. frontal lobe b. parietal lobe c. occipital lobe d. temporal lobe

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4. The pons is connected to the cerebellum by this band of white matter.

a. superior cerebellar peduncle b. decussation of pyramids c. tentorium cerebelli d. middle cerebellar peduncle

5. The vital centers for control of respiration, heart rate, and blood

pressure are located here. a. spinal cord b. medulla c. cerebrum d. cerebellum


1. b; 2. b; 3. a; 4. d; 5. b

Go on to Lesson 14.

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Lesson 14 Peripheral Nervous System

Reading Assignment

Read Chapter 14 in your textbook. As always, study the figures

thoroughly and let the objectives guide your reading.

Objectives


1. List all twelve cranial nerves and the part of the brain or brainstem

associated with each. Briefly, describe the structures innervated by

each. Classify cranial nerves as primarily sensory, primarily motor,

or mixed. (See Tables 14.2, 14.3, and Table 2 in the Discussion

section of this lesson.) Also name the 31 pairs of spinal nerves

(Figure 14.6)

2. Describe the typical spinal nerve (see Figures 14.2 and 14.7), its

dorsal and ventral roots, and its dorsal and ventral rami. Discuss

the relationship between ventral rami and intercostal nerves and

plexuses. Identify body regions innervated by nerves from each

plexus.

3. Describe the concept of a plexus. Identify ventral rami of spinal

nerves that contribute to each plexus (see Figures 14.8–14.13 and

Tables 14.4–14.7). Know which plexus each of the following nerves

arise from and the muscular innervations of each nerve and plexus:

phrenic, ulnar, median, axillary, musculocutaneous, radial, femoral,

obturator, superior gluteal, inferior gluteal, tibial, peroneal

(fibular), pudendal.

4. Trace a nerve impulse from the spinal cord to the brachialis muscle;

note important anatomical structures and landmarks that the

impulse passes on its way to the brachialis muscle.

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5. Define dermatome and state its clinical importance (see Figure

14.14).

6. Describe the effects of peripheral nerve section to the following

nerves: radial, median, ulnar, femoral, tibial, peroneal (fibular).

Discussion

Inspect Figure 14.6. You will observe that there are 31 pairs of

spinal nerves. These are the nerves that emerge from the intervertebral

foramina. There are eight cervical, 12 thoracic, five lumbar, five sacral and

one coccygeal. Spinal nerves are named for the vertebrae below until the

eighth cervical spinal nerve (C8). C8 spinal nerve is between C7 vertebra

and T1 vertebra. (There is no C8 vertebra.) Once past C8, the naming

convention changes; spinal nerves from the first thoracic (T1) down are

named for the vertebra above their exit. This is why there are eight cervical

spinal nerves but only seven cervical vertebrae.

Study Tables 14.2 and 14.3. You have to know the general (and

most significant) functions of each cranial nerve and the areas of the brain

or brainstem the nerve originates from. Your book gives far more

information than you need to know, so I have summarized the information

you need to know in this course in Table 1 in this lesson. (You should still

read the material in the book, naturally.) I tend to use action words to help

remember functions. The cranial nerves should be thought of as twelve

additional pairs of spinal nerves for our purposes.

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Table 1. Cranial Nerves

Brain/ Brainstem Origin Cranial Nerve Function

CEREBRUM 1. olfactory smell 2. optic vision MIDBRAIN 3. oculomotor moves eye muscles, visceral

motor to pupil 4. trochlear moves eye muscles PONS 5. trigeminal moves muscles of chewing;

sensory to front of head 6. abducens motor to eye muscles 7. facial moves facial muscles (smiling,

etc.), tastes, salivates, cries PONS AND MEDULLA 8. vestibulocochlear hears, monitors balance MEDULLA 9. glossopharyngeal swallows, tastes, salivates,

monitors blood pressure 10. vagus swallows, tastes, some motor to

muscles of speech, parasympathetic, most of the ventral body cavity (viscera)

11. accessory turns the head (sternocleidomastoid muscle) and shrugs the shoulder (trapezius) muscles

12. hypoglossal moves the tongue

Next, consider Figures 14.2 and 14.7. The diagrams portray a spinal

nerve from formation to division into two branches, called rami. Spinal

nerves are formed when two roots, one ventral and one dorsal, come

together. The ventral root is motor; the dorsal root is sensory. Once the

two roots have jointed, you have a spinal nerve. From this point on, the

nerve is also considered a mixed nerve, mixed in the sense that it has

both sensory and motor components (fibers). After spinal nerves have

exited the intervertebral foramina, they split—one branch going forward,

one backward. These branches have names: the first is the ventral ramus,

the other one is the dorsal ramus. Do you think the rami are motor only,

sensory only, or mixed?

Dorsal rami innervate the muscles of the deep back (e.g., erector

spinae) and provide sensory innervation to the back. Verntral rami can do

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one of two things. They either become intercostal (between the ribs)

nerves or they enter into plexuses. There are four major plexuses.

A plexus is a network of nerves that begins with ventral rami. They

combine and recombine and eventually result in distinct nerves. Study of

Tables 14.4 through 14.7 and Figures 14.8 through 14.13. Identify muscle

groups innervated by each plexus (e.g., nerves from the brachial plexus

innervate muscles of the shoulder girdle and upper extremity and provide

sensory/cutaneous innervation of the upper extremity). Next, identify

muscle groups innervated by specific nerves and plexuses listed in

Objective #3. For example, the radial nerve innervates muscles of the

posterior arm and forearm (these muscles generally extend the forearm,

wrist, and digits).

Study each plexus and note the ventral rami of spinal nerves that

contribute to each. An unfortunate convention is that the ventral rami that

contribute to the formation of a plexus are called roots. The word "roots"

here does not refer to ventral and dorsal roots that combine to form spinal

nerves. Note—you do have to remember the nerves that arise from the

plexuses. (By the way—the answer to the question posed a couple of

paragraphs above is that ventral and dorsal rami are mixed. Any nerve

peripheral to the intervertebral foramen is mixed.)

To summarize, the cervical plexus is formed by ventral rami of

spinal nerve C1–5. The brachial plexus receives contributions from ventral

rami of C5–T1. The lumbar plexus is formed from spinal nerves L1–L4. L4

overlaps into the sacral plexus, which receives contributions from L4–S4

spinal segments. Remember to identify the nerves in Objective #3 and the

plexus of origin for each.

I have attempted to summarize and simplify nervous innervations

in Table 2.

Table 2. Nervous Innervations

Nerve Area

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Nerve Area Dorsal Rami Muscles of the deep back Phrenic Diaphragm Intercostals Intercostal muscles, muscles of the abdominal

wall Pectoral nerves Pectoral muscles Dorsal Scapular Rhomboids and levator scapulae Suprascapular Supraspinatus, Infraspinatus Thoracodorsal Latissimus dorsi Long Thoracic Serratus anterior Axillary Deltoid, Teres minor Ulnar 1½ muscles of the anterior forearm and intrinsic

muscles of the hand (all digits except thumb) Subscapular Subscapularis, Teres major Radial (includes branches

that become posterior interosseous nerve)

Muscles of the posterior arm and forearm

Musculocutaneous Muscles of the anterior arm Median Muscles of the anterior forearm and thumb Femoral Muscles of the anterior thigh Obturator Muscles of the medial thigh Inferior gluteal Gluteal muscles Superior gluteal Gluteal muscles Tibial (includes sciatic

innervations) Muscles of the posterior thigh and leg

Peroneal (fibular nerve) Muscles of the lateral and anterior leg Pudendal Perineum (floor of pelvis)

The fourth objective asks you to trace a nerve impulse from spinal

cord to brachialis muscle. If you understand this pathway, you should be

able to trace a nerve impulse from the spinal cord to any of the muscles

you learned in the muscle system lesson. The pathway to the brachialis

muscle is as follows:

Anterior gray horn of spinal segments C5–T1 to anterior roots of

spinal nerves C5–T1 to join posterior roots of spinal nerves C5–T1 to form

spinal nerves C5–T1 to ventral rami of spinal nerves C5–T1 to form "roots"

of brachial plexus. The impulse then negotiates trunks–divisions–cords of

the plexus to eventually form five terminal nerves of the brachial plexus

(among these is the musculocutaneous nerve, which innervates the

Brachialis muscle).

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As you might surmise, spinal cord damage is far more serious than

trauma to a single peripheral nerve. With the latter, only the muscles and

skin innervated by the damaged nerve will be affected. Review the clinical

applications in Chapter 14 that describe the motor impairment that would

result if median, ulnar, radial, femoral, tibial, or peroneal (fibular) were

damaged. Even if the damaged nerve is a major one, the extent of the

symptoms will be far less than with a spinal cord injury. Furthermore, a

severed peripheral nerve is likely to repair itself, whereas the spinal cord

does not.

Sensory fibers are attached to receptors of various kinds. In

particular, a map of innervation by sensory fibers has been developed on

the surface of the body. Each segment of the spinal cord is responsible,

through its sensory fibers, for supplying a part of the surface of the body.

The skin supplied by the spinal cord segment is referred to as a

dermatome. Dermatomes can be used to determine the extent of spinal

cord injury. A map of the dermatomes is shown in Figure 14.14.

Sample Questions

1. Which of the following is composed of sensory fibers only? a. ventral roots of spinal nerves b. ventral rami of spinal nerves c. dorsal roots of spinal nerves d. dorsal rami of spinal nerves

2. What is the name given to a collection of nerve cell bodies outside the

CNS? a. ganglion b. horn c. tract d. nucleus

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3. How many pairs of cervical spinal nerves are there? a. 5 b. 8 c. 10 d. 12

4. Identify the nerve injured if a patient is unable to move his thumb.

a. ulnar b. median c. axillary d. radial

5. The phenic nerve develops from this plexus.

a. sacral b. lumbar c. brachial d. cervical


1. c; 2. a; 3. b; 4. b; 5. d


Instructions



Assignments."

Description


1. Trace a nervous impulse from the spinal cord to the rectus femoris

muscle, noting different nervous tissue structures the impulse will

have to negotiate along the way. (A couple of tips: you will have to

start by looking up, in Chapter 11, the nerve that innervates the

rectus femoris muscle. Start at the anterior gray horn of the spinal

cord; then trace the impulse out the intervertebral foremen and

through the appropriate plexus.)

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2. Define a nerve plexus. List spinal nerves that contribute to the

formation of the four major plexuses. Generally, describe muscle

groups innervated by nerves from each of the plexuses. Identify the

anatomical location where each plexus is found.

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Lesson 15 Autonomic Nervous System

Reading Assignment

Let the objectives guide your reading of Chapter 15 in your

textbook. There is a lot more information in the chapter than you are

required to know, but do make sure to give the chapter at least one

complete reading.

Objectives


1. Contrast autonomic and somatic systems (see Figure 15.2). Define

anatomical differences between sympathetic and parasympathetic

divisions of the autonomic nervous system (see Table 15.1).

2. Locate ganglia for the ANS: pre-vertebral (peripheral) ganglia,

sympathetic trunk, and terminal ganglia (Figures 15.5 and 15.7).

3. Locate the adrenal medulla (Figure 15.7) and explain its

relationship to the ANS.

4. Describe the possible fates of pre-ganglionic sympathetic axons.

Define white and gray rami communicans (see Figures 15.9–15.13).

5. Know the general effects of sympathetic and parasympathetic

innervation of visceral effectors listed on Table 15.2.

6. List "higher centers" that influence the autonomic nervous system.

7. Describe the role and location of visceral sensory/afferent neurons.

Define referred pain.

Discussion

Much of what you have to accomplish relates to comparing the

autonomic nervous system (ANS) to the somatic system and comparing

the two components of the ANS to one another. We will begin by

comparing the ANS to the somatic system.

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If you recall, the somatic motor system is responsible for

innervation for voluntary muscle (skeletal muscle). By contrast, the ANS is

responsible for innervation of involuntary muscle (smooth and cardiac

muscle). The somatic system is a one neuron system. That is, an axon from

a motor neuron cell body (located in the anterior gray horn of the spinal

cord) travels directly to the muscle it is to innervate before forming a

neuromuscular junction with the muscle cell. The ANS is a two neuron

motor system. The first neuron cell body is located in the central nervous

system. An axon from the first neuron synapses on the second neuron in a

peripheral ganglion; then an axon from the second neuron proceeds to the

muscle to be innervated. Some of these differences are illustrated in Figure

15.2

Another difference between the somatic system and ANS is that the

neurotransmitter substances differ. The transmitter substance for the

somatic system is always acetylcholine (ACh). The transmitter for the ANS

can either be ACh or norepinephrine. Lastly, somatic stimulation is always

excitatory; ANS innervation may lead to excitation or inhibition of the

involuntary muscle.

Now study Figures 15.5 and 15.7 and Table 15.1 for graphic and

verbal summary of the differences between the sympathetic and

parasympathetic divisions of the ANS. Note the following key differences:

1. origin of the preganglionic neurons for each division and 2. location of

the peripheral ganglia for each division. In sum, a pathway within the ANS

will have three components: preganglionic neurons, autonomic ganglia

and postganglionic neurons, and effectors (involuntary muscle).

Part of the adrenal gland, the adrenal medulla, can be included in

the sympathetic division of the ANS. The adrenal medulla secretes

epinephrine (and norepinephrine) into the bloodstream with effects

almost identical to sympathetic stimulation. The widespread activation of

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a sympathetic response is partly attributable to the rapid distribution of

hormones from the adrenal medulla in the bloodstream.

Now let's briefly take a closer look at the location of the ganglia in

each division. Return to Figures 15.5 and 15.7. Note that sympathetic

ganglia lie in one of two places. They are either close to the spinal cord in a

structure called the sympathetic trunk (alongside the vertebral column)

but a few are located peripherally, in front of the vertebral column (and

the CNS). The latter are referred to as pre-vertebral (peripheral) ganglia.

Regardless, sympathetic ganglia are relatively close to the vertebral

column (and the CNS). Examine Figure 15.7 to confirm this point. Notice

that the ganglia for the parasympathetic division (called terminal ganglia)

are almost all situated on or close to the structure to be innervated, quite

distant from the CNS.

We earlier noted that the two divisions employed different

transmitter substances. Specifically, the parasympathetic division uses

only ACh as a transmitter substance. The sympathetic division's

transmitter substance will vary depending on whether the synapse is

between preganglionic axon and postganglionic neuron or between

postganglionic axon and involuntary muscle. In the case of the former, the

transmitter substance is also ACh. But with the second synapse

(neuromuscular junction) the transmitter substance is almost always

norepinephrine. ("Almost" because there are a few exceptions where the

transmitter substance at the sympathetic division's postganglionic

neuron's synapse with the smooth or cardiac muscle is also ACh.) Figure

15.4 summarizes transmitter substance similarities and differences

between the two divisions.

For most organs and viscera, the ANS supplies dual innervation.

That is both sympathetic and parasympathetic divisions innervate

effectors. The result of dual innervation could be antagonistic (opposite) to

one another, complementary, or cooperative.

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Figures 15.9–15.13 illustrate the three possible fates of

preganglionic sympathetic axons. They can do any of the following:

1. Synapse on the sympathetic trunk and be distributed with a spinal

nerve at the same spinal segment;

2. Synapse at a higher or lower level of the sympathetic trunk and be

distributed with a spinal nerve at a different spinal segment; or

3. Pass through the sympathetic trunk and become a splanchnic nerve

to one of the three peripheral ganglia anterior to the vertebral

column (e.g., celiac). See Figure 15.7.

When you are comfortable with the materials we have covered so

far, turn to Table 15.2. Objective five requires you to know the general

effects for the sympathetic and parasympathetic stimulation. If you look

over Table 15.2 a couple of times, you should get the sense that the

sympathetic division usually produces a response in the organ or structure

innervated consistent with meeting an emergency. Conversely, the

parasympathetic division almost always results in a rest and recovery

response in the structure innervated. These general effects are consistent

with the primary purposes of each division. The sympathetic division is

concerned with responses to emergency situations, often called the "fight

or flight response." Energies and resources within the body are mobilized

for action. In contrast, the parasympathetic division seeks to conserve

energy and take care of routine, but necessary, "housekeeping" chores that

must be done for the body to function properly on a day-to-day basis.

Hence, if you think of what you would want the organ to be doing in an

emergency, you will usually be able to deduce the sympathetic effect on the

organ. The parasympathetic effect is generally the opposite, or it has no

effect on the organ or tissue.

Higher control of the ANS is exerted mostly through the

hypothalamus, reticular formation in the brainstem, and control centers in

the medulla oblongata, but several other structures have lesser effects. The

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anterior nucleus of the thalamus and the cerebral cortex can have some

effect on the ANS.

Although the majority of discussion of the ANS features its visceral

motor functions, visceral sensory neurons do exist and it is clear we can

feel some modalities in visceral structures (especially temperature and

pain). However, unlike the clear anatomical differences between visceral

motor neurons, it turns out that visceral sensory neurons are found in the

same location as somatic sensory neurons—in the dorsal root ganglia. One

notable difference between somatic sensory and visceral sensory systems

does exist: the concept of referred pain. Whereas pain associated with

somatic sensory receptors is projected to its actual physical location (e.g.,

pain from a cut finger), with the visceral sensory system it is projected to

an area of the body that does not always correspond to the visceral organ

(e.g., pain associated with a heart attack). (See Figure 15.15.)

Sample Questions

Try these after you believe you have mastered the material covered

in the objectives.

1. Which statement concerning the ANS is not true? a. It usually operates without conscious control. b. It regulates visceral activities. c. All of its axons are afferent (sensory) fibers. d. It contains ganglia.

2. Control of the ANS is exerted by all but which of the following?

a. medulla oblongata b. hypothalamus c. filum terminale d. thalamus

3. Axons from preganglionic neurons of the parasympathetic division of

the ANS synapse here. a. sympathetic chain ganglia b. peripheral ganglia c. terminal ganglia

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d. dorsal root ganglia

4. Which is not part of the fight or flight response? a. dilation of the pupils b. increased heart rate c. constriction of blood vessels in the viscera d. contraction of the urinary bladder

5. Preganglionic fibers of the sympathetic division tend to be shorter than

postganglionic fibers for this reason: a. their ganglia lie closer to the vertebral column. b. they have gray rami communicantes. c. they do not synapse with splanchnic nerves. d. they have to synapse on more postganglionic neurons.


1. c; 2. c; 3. c; 4. d; 5. a


Instructions



Assignments."

Description


1. Identify and explain the principle differences between the voluntary

nervous system and autonomic nervous system.

2. Define autonomic ganglion? Describe the location and function of

the three types of autonomic ganglia. Define and discriminate white

and gray rami communicantes.

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Lesson 16 Special Senses

Reading Assignment

Read Caper 16 in your text. Use the objectives below to help identify

important information in the chapter.

Objectives


1. Contrast general sensory receptors and special sensory receptors.

2. Describe the microscopic anatomy of receptors for taste and smell.

Summarize their neural pathways and the cranial nerves involved.

3. Identify the anatomy of the eye, including lacrimal gland, tunics

(fibrous, vascular, sensory), anterior chamber (glaucoma), posterior

chamber, lens (cataract).

4. Describe the neural pathway for vision: retina, optic nerve, optic

chiasma, optic tract, thalamus, optic radiations, visual cortex.

5. Identify the anatomy of hearing and balance.

! Outer ear—external auditory meatus, tympanic membrane

! Middle ear—ossicles, pharyngotympanic tube

! Inner ear—semicircular ducts, utricle, saccule, cochlear duct,

spiral organ (of Corti), helicotrema

6. Summarize the neural pathways for hearing and balance.

Discussion

Special senses, suchas vision and hearing, distinguish themselves

from general sensory receptors on the basis of two main differences. First

of all, general sensory receptors are spread throughout the body—e.g.,

receptors for touch are found everywhere. In contrast special senses are

resticted to the head region. Secondly, special sense information is

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transported by way of cranial nerves, not spinal nerves, as are most

general senses.

Smell and taste are two special senses that are quite old from the

point of view of evolution—most mammals are able to smell and taste. In

fact, in lower species these two modalities are primary methods through

which the creature understands the environment. Taste and smell are

preserved in the human species, but are not as vital to interpretation of the

environment as with lower species.

Smell receptors are located primarily in the upper nasal mucosa

and nasal septum (the cartilage that separates the two nasal cavities).

Figure 16.3 displays olfactory receptors and the formation of the olfactory

nerve (first cranial nerve) from the convergence of olfactory receptor cell

fibers. The olfactory nerve transmits the smell information to the olfactory

cortex (see Figure 13.23b). Of course, the olfactory nerve and smell

information are involved in the primitive limbic system discussed earlier

in this unit.

In contrast, taste is monitored by three cranial nerves—the facial,

glossopharyngeal, and the vagus (cranial nerves 7, 9 and 10 respectively).

However, all three cranial nerves feed taste information into a common

nucleus (the solitary nucleus) in the medulla (see Figure 16.2). From there

taste information has a mandatory synapse on the thalamus and then is

projected to the gustatory cortex on the inferior part of the post-central

gyrus (see Figure 13.23a). As you can observe in Figure 16.2, taste

receptors are embedded in the tongue and pharynx.

Vision is a sensory modality that would be difficult to do without.

Extra-ocular muscles (see Figure 16.6) allow us to voluntarily direct our

gaze in a variety of directions to take in visual-sensory information about

the environment. The anatomy of the eye is provided in Figure 16.7. The

eye is divided into two distinct areas delineated by the anterior and

posterior chambers. The anterior chamber is filled with a fluid substance,

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the aqueous humor. It is produced and drained on an on-going basis.

(Failure to drain enough aqueous humor from the anterior chamber

results in a build-up of pressure that can damage the eye permanently—

glaucoma). In contrast the posterior chamber is filled with a firmer, gel-

like matrix known as the vitreous humor. It is stable and does not need to

be replaced constantly. The vitreous humor gives a stable form and shape

to the eye.

The interior of the eye is lined with three layers or tunics. An outer

fibrous tunic is composed of the sclera posteriorly and the cornea

anteriorly. The anterior cornea is transparent and allows light to pass

through.

The intermediate tunic likewise has an anterior part (the ciliary

body) and a posterior part (the choroid). A part of the ciliary body, the

ciliary zonule, allows the smooth muscle of the ciliary body to adjust the

concavity/convexity of the lens so that light passing through the opening

(the pupil) will strike the sensory receptor for light in the deep tunic (the

retina) and be detected. It is the diameter of the pupil that automatically

adjusts to illumination by constricting or dilating.

The third tunic of the eye is the retina, containing two layers. One of

the layers of the retina contains sensory receptors for light and is called the

neural layer. Fibers from a variety of different types of sensory cells in the

retina pass posteriorly and converge to form the optic nerve (second

cranial nerve). Figure 16.10c shows the fibers converging on the posterior

pole of the eye to form the optic nerve.

Figure 16.15 illustrates the pathway for light information from the

retina to the visual cortex of the occipital lobe of the cerebral cortex.

Objective four lists the structures of the visual pathway in correct order.

You should remember these structures. A point of clarification about

vision though, because cerebral control is contralateral the left visual field

is seen on the right occipital lobe and vice-versa. Further, since one-half of

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each visual field is seen on each retina, the halves of the visual fields must

unite at some point along the way to the visual cortex. This occurs at a

structure called the optic chiasma, where fibers of the inside halves of the

right and left optic nerves cross to the opposite side (illustrated in Figure

16.14). After the fibers have crossed and the left and right visual fields are

completed, the name of the fibers changes to optic tract (from the previous

optic nerve). Following a synapse on the thalamus (remember that all

information accessing the cerebrum must synapse on the thalamus), visual

information is projected to the visual areas on the occipital lobe by way of

optic radiations, completing the pathway for vision.

The sensory receptors for hearing and balance are situated close to

one another in the inner ear. Therefore, it is not unusual for a person who

has a hearing deficit involving the inner ear to also manifest a balance

problem. This is particularly common among older adults and may add to

the risk of sustaining a serious injury from a fall.

The outer ear (see Figure 16.16) consists of a long canal, the

external auditory meatus that ends internally at the tympanic membrane.

Its role is to transmit auditory sensations, which are vibrations in the air.

These vibratory pulsations cause the tympanic membrane to more back

and forth.

Anchored to the tympanic membrane are three small bones, the

auditory ossicles (see Figure 16.16). Between the ossicles are joints that

move in response to movements of the tympanic membrane. One of the

auditory ossicles (the stapes) rests against the oval window of the inner

ear. A pharyngotympanic (auditory) tube connects the throat (pharynx) to

the middle ear. As an aside, the infections that affect many children as

otitis media (an "ear infection") find origin in the pharynx and travel up

the tube to spread the infection to the middle ear.

The inner ear consists of sensory receptors for hearing and balance.

Those for balance are the utricle, saccule and semicircular ducts (see

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Figures 16.18 and 16.21).The utricle is the receptor for linear movement of

the head (as in flexing and extending/nodding the head "yes"). The saccule

allows us to maintain orientation against gravity—static equilibrium. The

semicircular ducts monitor rotational/angular acceleration of the head (as

in rotating the head, or shaking the head "no"). All of the receptors

function in about the same way (see Figures 16.21, 16.22), where a material

(e.g., otolithic membrane, cupula) lags behind a movement of the head.

Eventually the material moves but with some latency compared to the

movement of the head. Once the material moves, it stimulates receptor

hair cells, and then the fibers of the vestibular part of the eighth cranial

nerve.

The neural pathway for balance does not travel to the cerebrum for

the most part, as with most other sensory modalities. Instead, balance

information travels to vestibular nuclei in the medulla oblongata and the

cerebellum.

Detail of the auditory portion of the inner ear is illustrated in Figure

16.23. But perhaps a better way to understand the cochlea is displayed in

the Figures 16.16, 16.19 and 16.23. The stapes causes vibrations against the

oval window, which in turn causes vibrations in the fluid (perilymph) of

the scali vestibule. The vibrations are further conveyed from the scali

vestibule to the fluid (endolymph) of the cochlear duct. These vibrations

cause the basilar membrane inside the cochlear duct to vibrate,

stimulating receptor hair cells for hearing (for a closer view see Figure

16.19). Once the hair cells bend the cochlear portion of the eighth cranial

nerve is stimulated.

Unlike, balance information, auditory information is conveyed to

the cerebral cortex (primary auditory area on the temporal lobe) after a

synapse on the thalamus. Compared to vision, where all impulses from the

retina on one side travel to the opposite cerebral hemisphere, auditory

information from each ear travels to each hemisphere. This is why a

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person can still hear in both ears even though trauma (e.g., a stroke) may

destroy the primary auditory cortex on one cerebral hemisphere. However,

as mentioned in the lesson on the CNS, damage to language areas on the

dominant hemisphere will result in difficulty using language (aphasia)

even though the person can hear.

Sample Questions

Try these after you believe you have mastered the material covered

in the objectives.

1. Where are sensory receptors for smell located? a. vomer b. nasal mucosa c. palate d. pharynx

2. Which cranial nerve does not carry sensory information for taste?

a. facial b. glossopharyngeal c. trigeminal d. vagus

3. This part of the fibrous tanic of the eye is white, tough, and opaque. a. cornea b. choroid c. sclera d. retina

4. This part of the ears contains the auditory ossicles. a. external b. middle c. internal

5. The stapes transmits vibrations against the oval window of the inner ear, causing this to move. a. utricle b. perilymph c. saccule d. tectarial membrane

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1. b; 2. c; 3. c; 4. b; 5. b

Go on to Lesson 17.

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Lesson 17 Endocrine System

Reading Assignment

Read Chapter 25 in your textbook. As always, use the objectives to

key your reading.

Objectives


1. Define and differentiate exocrine and endocrine glands.

2. Identify and locate the major endocrine glands (see Figure 25.1).

3. Define the three basic types of hormones: steroids, proteins, and

amines.

4. Describe control of hormone secretion by negative feedback

mechanisms and neural control pathways. Also, define the three

mechanisms for control of hormone release (humoral, neural,

hormonal—see Figure 25.2).

5. Generally describe how nervous and endocrine systems interact at

the pituitary gland (hypophysis) and hypothalamus.

6. List the hormones of each of the following endocrine glands and

their general effects: pituitary (hypophysis), thyroid, parathyroids,

adrenals, pancreas, ovaries, testes, and thymus.

7. Describe the etiology of diabetes mellitus (Type I and Type II) and

contrast it with diabetes insipidus.

Discussion

Hormones are blood-borne molecules that travel to certain cells

and cause a physiologic response. Endocrine glands do their work by

secreting hormones that travel in the bloodstream and influence other

cells to perform certain physiological tasks, increase or decrease the speed

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of a certain process or cause other endocrine glands to secrete yet other

hormones. Hormones eventually find their way into the blood stream

where they can move more quickly to their target cells—the cells that

respond to the hormone. The aim of the endocrine system and its

hormones is to maintain homeostasis, all things functioning normally and

in a well-adjusted fashion in the body's internal environment.

Endocrine glands contrast with a second type of gland in several

ways. Exocrine glands never secrete hormones, their products tend to be

substances such as oil, sweat, enzymes, etc. Exocrine gland products are

secreted onto epithelium, tubes, body cavities, or covering and lining

epithelium. For example, sweat is secreted onto the skin, covering

epithelium. Because of this, secretions from one exocrine gland do not

have a widespread effect relative to the hormones of an endocrine gland.

Hormones are distributed widely via the vascular system.

Endocrine glands tend to operate by way of a negative feedback

loop. This means they operate just like the thermostat in your house. If the

temperature falls, the thermostat detects it and turns on the furnace.

When the temperature increases to an acceptable level, the thermostat

causes the furnace to turn off. Decreases in temperature bring about (the

opposite) an increase in the activity of the furnace (and vice versa).

Likewise, presence or absence of certain products or substances in

the blood stream are detected by the endocrine gland, causing hormone

secretion to turn on or off, according to need. In this way, the internal

environment of the body is kept in proper working order—in balance, in

homeostasis. This sort of feedback control is characteristic of humoral

control of hormone release (see Figure 25.2). Besides humoral control,

endocrine glands may be controlled by other (tropic) hormones secreted

by the pituitary gland, or by direct nervous stimulation called hormonal

and neural control respectively (see Figure 25.2).

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Identify the major endocrine glands in Figure 25.1. You should be

able to locate all of the glands and give an anatomical description of where

each is found.

Hormones are of three basic types: steroids, proteins, or amines.

The hormones differ in how each brings about changes in target cells.

Steroid hormones can enter target cells and alter protein synthesis within

the cell.

Protein and amine hormones bind with receptor sites on the target

cell membrane causing changes in the cell membrane, which in turn may

cause changes in a variety of inter-cellular activities.

Perhaps the single most important endocrine gland is the pituitary

(also called the hypophysis, sometimes called the "master" endocrine

gland). It is located in the sella turcica of the sphenoid bone. The pituitary

can actually be thought of as two glands in one, the anterior (also called

the adenohypophysis) and posterior (also called the neurohypophysis)

pituitary glands. The pituitary and hypothalamus represent the meeting of

the nervous system and the endocrine system. This is more than just a

meeting, however, because the hypothalamus can have a great influence

on the pituitary gland. The hypothalamus and the pituitary are portrayed

in Figures 25.3 through 25.5.

The hypothalamus exerts much of its control over the anterior

pituitary (adenohypophysis) through the use of releasing factors.

Releasing factors pass from the hypothalamus to the anterior part of the

pituitary via blood vessels in the infundibulum and cause the anterior

pituitary to secrete its hormones (see Figure 25.4). Some of the pituitary

hormones then act on target cells that are non-specific. That is, growth

hormone stimulates many different cells to grow: bone, muscle, or fat

tissue. In contrast, the anterior pituitary also secretes a series of hormones

that act on still other endocrine glands. The target cells for these hormones

are other glands. The second group of hormones are referred to as tropic

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hormones. For example, thyroid stimulating hormone is a tropic hormone

because it stimulates the thyroid gland. Table 25.1 lists the primary actions

of the hormones of the pituitary. See Figure 25.4 for the relationship

between the anterior pituitary and the hypothalamus.

Turning to the posterior pituitary, (neurohypophysis) we find that it

secretes only two "hormones," oxytocin and antidiuretic hormone (ADH).

Closer inspection of the posterior pituitary (see Figure 25.5) reveals that

axons from the hypothalamus extend through the infundibulum into the

posterior pituitary. As a result, oxytocin and antidiuretic hormone are

actually closer to neurotransmitter substances, manufactured in the

hypothalamus, transported to the posterior pituitary and then secreted

into the bloodstream by the posterior pituitary. The supraoptic nucleus

produces ADH in the hypothalamus, while the paraventricular nucleus

produces oxytocin in the hypothalamus. Both are then secreted by the

neuro-hypophysis.

Study Table 25.1 and remember the major action of each of the

pituitary's hormones. To make your task a little easier, the tropic

hormones usually tell you a lot about where their target cells are. Use this

information to deduce each tropic hormone's effect. Also, for lutenizing

hormone and follicle stimulating hormone, just remember that they are

both involved in development of mature gametes (sperm cells or egg cells),

preparation for fertilization and gestation, and production of sex

hormones (estrogen and testosterone).

The thyroid gland is situated in the neck, anterior to the trachea,

superior to the sternum, and inferior to the larynx (see Figure 25.6). The

thyroid plays a major role in augmenting metabolic activity by controlling

the rate of metabolism. This is accomplished through the secretion of

thyroid hormones. A second hormone secreted by the thyroid is calcitonin.

Along with parathyroid hormone (discussed below), calcitonin regulates

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blood calcium levels. The presence of an adequate level of calcium in the

bloodstream is essential for life.

The parathyroid glands (there are usually four of them) are located

on the posterior surface of the thyroid (see Figure 25.7). Parathyroid

hormone is the only hormone produced and secreted by the parathyroid

gland. You should know how it acts to increase blood calcium: releasing it

from bone, stimulating its absorption in the digestive tract, and retaining

it through the kidneys. (Just for fun: can you remember the tissue we

discussed earlier that serves as a storage area for calcium?)

The adrenal glands sit atop the kidneys (see Figure 25.8); this is

why they are sometimes called the suprarenal glands. The adrenal gland is

a fairly complex structure, with three different zones or levels to its outer

shell (cortex), and a centrally located medulla (center). Each of these four

constituents gives rise to its own hormone. Read about each of these

hormones and their general effects in the textbook. With regard to the

adrenal medulla, some further comment is necessary. If you pay special

attention to the section on the adrenal medulla, you will find that

splanchnic nerves (preganglionic axons) from the sympathetic division of

the ANS innervate the adrenal medulla. Second, you will find that the

hormones secreted by the adrenal medulla produce the same effects as the

sympathetic division of the ANS. It is no coincidence that norepinephrine

is the transmitter substance for postganglionic axons of the sympathetic

division of the ANS and also a hormone secreted by the adrenal medulla.

In a sense you might think of the adrenal medulla as yet another ganglion

that preganglionic fibers from the sympathetic division of the ANS can

synapse on.

The pancreas is involved in the regulation of blood glucose (sugar).

It is pictured in Figures 25.1 and 25.10. It is located posterior to the

stomach and first part of the small intestine, the duodenum. The pancreas

is part exocrine gland, concerned with the secretion of digestive enzymes.

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But its endocrine functions command our attention for the purposes of the

present lesson. It secretes two hormones that produce opposite effects.

Insulin decreases blood glucose, while glucagon increases blood glucose.

Insufficient or absent secretion of insulin results in diabetes mellitus, with

the familiar excess of glucose in the bloodstream and urine.

The ovaries (female) and testes (male) together are referred to as

the gonads. You can locate each of the gonads on the composite Figure

25.1. The gonads secrete what are generally known as sex hormones

(testosterone in the male; estrogen and progesterone in the female). In

general, sex hormones control secondary sex characteristics (placement of

hair, relative amounts of muscle and fat, weight of skeleton, etc.),

stimulate maturation of gametes (egg cells and sperm cells), and promote

activities that support pregnancy.

The thymus gland (see Figure 25.1) is located posterior to the

sternum in the upper center portion of the chest. The thymus gland is not

well understood, but it has been implicated in the body's immune system.

Its major role seems to be production of a specialized white blood cell

known as a T-lymphocyte. Because of its role in the immune system, the

thymus gland and T-lymphocytes are among the most studied tissues in

AIDS research.

Sample Questions

1. This name is given to a hormone that acts on another endocrine gland. a. feedback hormone b. acceleratory hormone c. tropic hormone d. inhibiting hormone

2. Which endocrine gland listed below is most closely related to the

sympathetic division of the ANS? a. pancreas b. adrenal medulla c. parathyroid

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d. thyroid

3. Why is the posterior pituitary not a typical endocrine gland? a. It receives a rich blood supply. b. It does not make its own hormones. c. It is not near the brain. d. It contains ducts.

4. Name the antagonistic hormones that regulate blood calcium.

a. insulin-glucagon b. aldosterone-cortisone c. PTH-calcitonin d. HGH-ADH

5. Hypophysis is another name for this gland.

a. pituitary b. testes c. pancreas d. thyroid


1. c; 2. b; 3. b; 4. c; 5. a

Examination #3

Examination #3 follows Lesson 17. This will be a one-hour,

supervised examination. No books, notes, or other aids may be brought to

the exam. The examination consists of forty multiple-choice questions of

the same type you have seen in the sections of sample questions in each

lesson. The exam questions are allocated according to the number of

objectives per topic.






version only).

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UNIT 5 VISCERAL SYSTEMS

Lesson 18 Heart

Lesson 19 Blood Vessels and Lymphatics


Lesson 20 Respiratory System

Lesson 21 Digestive System


Lesson 22 Urinary System

Lesson 23 Reproductive System

Examination #4

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Lesson 18 Heart

Reading Assignment

Read Chapter 18 in your textbook pertaining to the heart. You

might be surprised by the relatively few objectives for this important

organ. However, to answer each objective, you will have to know quite a bit

of information.

Objectives


1. Define the functions of the circulatory system. Also define atrium,

ventricle, systole, diastole, pulmonary circuit, and systemic circuit.

2. Describe the location of the heart in the mediastinum (see Figure

18.2).

3. Identify the structure of the pericardium and heart wall (Figure

18.3).

4. Identify the sulci, chambers, great vessels and valves (and papillary

muscles) of the heart on both anterior, posterior, and internal views

(Figure 18.5).

5. Trace the course of a erythrocyte through the heart and lungs,

beginning at the right atrium and ending at the aorta. Define

structural and functional differences between the left and right

heart.

6. Identify the origin of the heart beat and the intrinsic conduction

system of the heart (Figure 18.14). Identify the effects of

sympathetic and parasympathetic stimulation of the heart (Figure

18.15).

7. Identify the major vessels of coronary circulation (Figure 18.16) and

the general areas each supplies or drains.

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8. Identify major risk factor for cardio-vascular disease. Define a

congestive heart failure, angina pectoris, ischemia, myocardial

infarction, incompetent valve, stenotic valve, and heart block.

Discussion

The circulatory system includes fluids, solid elements, tubes, and a

pump.

The circulatory system functions to transport gases and nutrients as

well as waste products. It carries hormones to target cells rapidly. And

because of the white blood cells (leukocytes) and platelets (essential for

clotting) in the blood, the circulatory system plays important roles in

defense of the body (immune response, clotting).

Blood is comprised of liquid (plasma) and solids (formed elements).

The formed elements are mostly cells that perform different roles within

the vascular system, though some of the cells may leave the blood stream

to do their job. The formed elements of blood usually compose about forty-

five percent of the total blood volume. This percentage is known as a

hematocrit.

The heart is located in the mediastinum, medial to each lung,

anterior to the vertebral column, posterior to the sternum. It is slightly off

center, to the left. The heart lies somewhat on its right side. It terminates

inferiorly in an apex (point) that is directed downward and to the left.

Notice that the four chambers of the heart, atria (2) and ventricles (2), are

not of equal size or presence. For example, most of the right ventricle is

seen in an anterior view of the heart (Figure 18.5b), but the largest

chamber, the left ventricle, makes up most of the left, inferior/posterior

surface of the heart (Figure 18.5d). Note also that most of the "great

vessels" enter or exit the heart at its superior border. Identify the aorta,

pulmonary trunk, superior vena cava, and inferior vena cava.

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The heart is surrounded by a triple-layered membrane, including

fibrous pericardium (see Figure 18.3). A space between the parietal and

visceral layers of the serous pericardium contains the pericardial fluid,

which serves as a lubricant and reduces friction as the heart beats. Hence,

the pericardial sac protects and stabilizes the heart in the mediastinum.

The wall of the heart is made up of an outer layer of epicardium.

Note that the epicardium is the same as the visceral layer of the serous

pericardium (see Figure 18.3). This is obviously not muscle, in contrast to

the second layer of the heart wall. The myocardium comprises the great

majority of the thickness of the heart wall, especially the ventricles. As you

might expect, it is comprised of cardiac muscle. Finally, there is an inner

layer of epithelium (known as endocardium) and connective tissue (elastic

and collagen fibers) that line the inner aspect of the heart's chambers.

The heart is a four-chambered pump (Figure 18.5e). The two upper

chambers are called atria (left and right atrium). There are walls (septa)

inside the heart dividing the atria from one another and the ventricles

from one another (interatrial and interventricular septa respectively).

However, the right atrium communicates with the right ventricle and the

left atrium communicates with the left ventricle. Each side of the heart

works as a unit (see Figure 18.6). The right (atrium and ventricle) side is

the pulmonary circuit (because it pumps blood to the lungs) and the left

side is the systemic circuit (because it pumps blood to the remaining

systems, e.g., digestive). Study Figure 18.5 to confirm the anterior,

posterior, and internal presentation of each chamber.

Also refer to Figures 18.5b and 18.5d to identify grooves on the

external surface of the heart, called sulci. One sulcus divides atria from

ventricles, the coronary sulcus. Another pair of grooves divides the

ventricles on the anterior and posterior surface of the heart, the anterior

and posterior interventricular sulci respectively. These landmarks are

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important to know because they divide the chambers of the heart and help

with identification of coronary blood vessels (covered below).

As we noted earlier, the atria communicate with the ventricles. They

do this through atrioventricular valves. The major valves of the heart are

shown in Figures 18.9 and 18.10. There are two atrioventricular valves, a

tricuspid valve on the right and a bicuspid/mitral valve on the left. Once

blood is pumped from atria into ventricles on each side, the tricuspid and

mitral valves prevent regurgitation of blood from the ventricles back into

the atria when the ventricles contract. Note, papillary muscles in the walls

of the ventricles attach to the valves by way of tendons, (chordae tendinae)

to help the valves resist the back flow of blood from ventricles into atria,

shown in Figures 18.5e and 18.9.

Notice a second set of valves in Figures 18.5e and 18.10. These

valves protect the opening between the right ventricle and pulmonary

artery and the opening between the left ventricle and the aorta. They are

collectively known as semilunar valves (pulmonary semilunar on the right;

aortic semilunar on the left). You should pay attention to the differences

between atrioventricular valves and semilunar valves. One major

difference is that the former have papillary muscles attached to them; the

latter do not.

The heart beat is said to be intrinsic; that is, it arises from a

structure located inside the heart itself. This structure is called the

"pacemaker," or more properly, the sinoatrial (SA) node. This node, along

with the others illustrated in Figure 18.14, cause the heart to beat. Study

the path of the bundles of fibers. They pass down the septum (wall)

separating the left and right ventricles and then swing lateral onto the

outer surfaces of each ventricle. This pattern suggests that the atria

contract from the top down, driving blood into the ventricles; whereas, the

ventricles contract from the bottom up, driving blood upward into the

pulmonary trunk (right ventricle) or the aorta (left ventricle). The

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autonomic nervous system (ANS) does innervate the heart (Figure 18.15)

and can cause it to increase rate and strength of contraction (sympathetic

effect) or decrease rate of contraction (parasympathetic effect).

ANS stimulation of the heart is controlled by "centers" in the

medulla (remember them when we talked about the brainstem?). There is

one center (cardioacceleratory) that will increase the rate and the strength

of the heart's contractions through the sympathetic division of the ANS.

Cardiac (sympathetic) nerves derived from upper thoracic levels of the

spinal cord stimulate the heart rate to increase and contract more

forcefully. A cardioinhibitory center has the opposite effect, slowing the

heart rate and decreasing the strength of contraction. Parasympathetic

(inhibitory) effects are produced primarily by way of innervation of the

heart by the vagus nerve (tenth cranial nerve).

As you already know, the heart is a muscle. All muscles need oxygen

and nutrients supplied via the bloodstream to do their work properly, so it

should come as no surprise to you that the heart receives a blood supply.

Coronary circulation (see Figure 18.16) begins with blood ejected from the

first part of the aorta (the ascending aorta) into the left and right coronary

arteries. The left coronary then gives off two major branches, a circumflex

and an anterior interventricular (between the ventricles). Likewise, the

right coronary has two branches, a marginal and posterior ventricular (see

Figure 18.16).

As a rule, coronary arteries supply any adjacent chamber or any

chamber they touch. For example, the anterior interventricular artery

supplies blood to two chambers it is adjacent to—the left and right

ventricles.

Once oxygen is depleted and blood in coronary circulation is ready

to return to the right atrium, it does so through the major venous channels

illustrated in Figure 18.16. The pattern is somewhat simpler for venous

return from coronary circulation than for arterial distribution. A great

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cardiac vein drains the anterior portion of the heart, a middle cardiac vein

drains the posterior aspect of the heart, and a small cardiac vein drains the

inferior-right portion of the heart. All three empty into the coronary sinus,

which in turn empties into the right atrium.

The basic pattern of heart action is as follows: the right heart

receives venous blood into the right atrium, pumps it into the right

ventricle where it is next pumped into the pulmonary trunk and arteries to

be passed on to the lungs. Oxygen is loaded onto red blood cells and

carbon dioxide removed in the lungs. The oxygenated blood returns to the

left atrium via pulmonary veins, then to left ventricle. Finally, the powerful

left ventricle drives oxygenated blood into the aorta for distribution

throughout the body (major circulatory routes will be discussed in the next

lesson). Note that while we have separated the pulmonary and systemic

parts of the heart's work, both are working concurrently. That is, blood is

being pumped through the pulmonary (right) side of the heart at the same

time different blood is being pumped through the systemic (left) side of

the heart.

Research and longitudinal studies of mortality in Western culture

point to heart disease and specifically heart attacks as one of the leading

causes of death. While some people are more predisposed to heart attacks

than others, it is mostly lifestyle risk factors that account for manifestation

of a heart attack: excess weight, hypertension (high blood pressure),

excessive saturated fats in the diet, smoking, diabetes mellitus, and lack of

regular exercise are the leading modifiable risk factors.

Look up the definitions for the remaining terms in objective

number 8 throughout the chapter.

Sample Questions

1. This atrioventricular valve is on the same side of the heart as the origin of the aorta.

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a. aortic semilunar b. tricuspid c. mitral d. pulmonary semilunar

2. Which chamber of the heart has the thickest walls?

a. right ventricle b. left ventricle c. right atrium d. left atrium

3. Which great vessel of the heart is associated with the right ventricle?

a. superior vena cava b. inferior vena cava c. aorta d. pulmonary trunk

4. Which of the following is not part of the heart wall?

a. pericardium b. epicardium c. endocardium d. myocardium

5. This vein empties de-oxygenated blood from coronary circulation into

the right atrium. a. great cardiac vein b. small cardiac vein c. middle cardiac vein d. coronary sinus


1. c; 2. b; 3. d; 4. a; 5. d

Go on to Lesson 19.

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Lesson 19 Blood Vessels and Lymphatics

Reading Assignment

Read Chapters 19 and 20 pertaining to the second part of our study

of the cardiovascular system, the blood vessels. As always, use the

objectives listed below to guide your reading.

Objectives


1. Describe the typical blood vessel in cross-section (see Figure 19.1).

Contrast the structure and function of elastic arteries, muscular

arteries, capillaries, and veins.

2. Discuss the problem of venous return to the heart. Identify the

relative allocation of blood volume in veins compared to arteries.

3. Identify principal arteries (see Figure 19.8) and veins (Figure

19.18):

a. Arteries: arch of the aorta and its major branches (Figure

19.9), arteries of the head and neck (Figure 19.10), arteries of

the upper extremity (Figure 19.11), major branches of the

abdominal aorta (Figure 19.12), and arteries of the lower

extremity (Figure 19.16). Skip branches of the thoracic aorta

and arteries of the pelvic region. See Figure 19.17 for a

summary.

b. Veins: veins draining the head and neck (Figure 19.20), veins

of the upper extremity (Figure 19.21), inferior vena cava and

azygos system (Figure 19.21) of veins of the thorax and

abdominal cavity (Figure 19.23), veins of the lower extremity

(Figure 19.25), and cerebral sinus drainage of the cranium

(Figure 19.20).

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4. Trace the circulation of a red blood cell from left femoral vein to left

femoral artery.

5. Trace the route of blood involved in hepatic portal circulation and

explain its importance (Figure 19.24).

6. State the functions of the lymphatic system.

7. List and define the components of the lymphatic system: lymph,

lymph capillaries (Figure 20.2), lymphatics (lymphatic collecting

vessels), lymph ducts, lymph nodes, spleen, thymus, and tonsils.

8. Describe the structure of a typical lymph node (Figures 20.4).

Identify the stroma and parenchyma of a lymph node.

9. Identify the thoracic duct, right lymphatic duct, and cisterna chyli

(Figure 20.3). Describe the general pattern of distribution of lymph

nodes in the body (Figure 20.3).

10. Describe, in general, the plan of lymph circulation from lymphatics

to the thoracic duct and right lymphatic duct to the subclavian veins

(see Figures 20.1 and 20.3).

11. Clinical applications: swollen lymph nodes, edema, monocucleosis,

Hodgkin's disease, AIDS.

Discussion

Just as a heart is likened to a pump, we can characterize the

vascular system as a vast network of tubes that deliver blood to various

destinations. The basic components of this tube system include: arteries,

which carry blood away from the heart; capillaries, which exchange

substances with tissues through their one-cell thick walls; and veins, which

convey blood back to the heart.

A closer look at arteries, capillaries, and veins in Figure 19.1 reveals

several marked structural differences throughout the tube system. A

typical artery has three layers: the first composed of epithelium (called

endothelium) and elastic tissue, the second composed of elastin and

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smooth muscle, and the third composed of elastic and collagenous

connective tissue. These layers are referred to respectively as tunica

intima, tunica media, and tunica externa. Two subtypes of arteries can be

derived from this basic three-layered arrangement, based upon the relative

amounts of connective tissue (especially elastic fibers) and smooth muscle.

The largest arteries lie close to the heart and are placed under the

greatest amount of stress because of the force of blood ejected by the left

ventricle. These large (elastic) arteries, in effect, "catch" the blood and

then recoil to propel the blood further along the arterial network. Large

arteries tend to have less smooth muscle.

Muscular or distributing arteries have considerably more smooth

muscle, though they are somewhat smaller than large elastic arteries. They

provide the greatest resistance to blood flow and are most influential in

determining blood pressure.

Capillaries are composed of a single layer of endothelium (Figure

19.1). This rather obviously makes it easier for substances to move into and

out of the capillary networks throughout the body. Capillaries unite to

form small, two-layered veins called venules so that blood may begin its

trip back to the heart.

Like arteries, veins have three tunics with names identical to those

of arteries. If you study Figure 19.1 and compare arteries and veins, you

will find that the walls of veins are thinner. This is attributable to less

smooth muscle and less elastic tissue in veins. The thin walls of veins are

consistent with the fact that there is far less force being exerted on the

veins. Blood pressure has dropped significantly by the time the blood has

traveled through the maze of arteries and the capillary bed to reach the

venous system. The thinner walls of the veins represent an adaptation to

the lower blood pressure and force behind the blood. Blood pools ("backs

up") in the venous system as a result.

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However, this presents a problem, particularly in the lower

appendages because blood must move toward the heart against gravity.

Part of the solution to this problem can be seen in Figure 19.6. Many veins

are outfitted with one-way valves, which resist the backflow of blood away

from the heart. As you can also see in Figure 19.6, skeletal muscle activity

exerts force on the "column" of blood in the vein and pushes it toward the

heart. The valves in veins assure that the blood will not lose the ground it

has gained, so to speak, and yield to the force of gravity.

Another part of the solution is that the venous system can

accommodate more blood than the arterial system because there are more

veins than arteries. There are both superficial and deep veins, whereas

there are only deep arteries.

Furthermore, the latter fact allows the venous system to

accommodate greater blood volume (about 65 percent) than the arterial

system.

Your textbook goes on to detail the main circulatory routes in the

body. You should have a general knowledge of the tissues that various

circulatory routes lead to. Try to approach the task of learning the selected

arteries and veins with a couple of things in mind. First, remember to test

yourself by photocopying the figures you need to learn, clipping off the

labels, and then trying to label the diagrams yourself. Second, realize that

blood vessels are frequently renamed as they move from one section of the

body to the next. Remember, you may have several names for the same

tube, depending on the part of the body you are talking about.

Begin with the aorta and its major branches shown in Figure 19.9.

Note that the aorta is divided into four sections: ascending, arch, thoracic,

and abdominal. Recognize the two coronary arteries are the first branches

off the (ascending) aorta. You do not have to know the small branches of

the thoracic aorta. But you should know the major branches of the

abdominal aorta (Figure 19.12). The celiac trunk and its branches supply

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the liver, spleen, stomach, and the first part of the small intestine. The

superior mesenteric sends arterial blood to most of (the remainder of) the

small intestines and proximal one-half of the large intestines. The inferior

mesenteric supplies blood to the distal one-half of the large intestines,

sigmoid colon, and rectum. Other branches are named for the organ

supplied—renals supply the kidneys, suprarenals supply the adrenal

glands, and gonadals supply ovaries or testes.

When you feel pretty confident about the arm (Figure 19.11), move

on to the lower extremity, illustrated in Figure 19.16. The abdominal aorta

ends by forming the common iliac arteries at the level of L-4 vertebra. The

common iliacs give a branch to supply the pelvic contents (the internal

iliac artery) and continue as the external iliac arteries on each side. Once

the external iliac passes into the lower extremities (under the inguinal

ligament), it is called the femoral artery. Try to label an unlabeled copy of

the same figure. Concentrate on the femoral, poplitial, anterior and

posterior tibial, fibular (peroneal) arteries. Also, identify dorsal pedis and

lateral and medial plantar arteries.

The arteries of the head and neck are pictured in Figure 19.9.

Arteries of the head and neck are branches off the external carotid and

pretty much tell you the tissue supplied in the name of the artery (e.g.,

facial artery supplies most structures of the face). The internal carotid and

vertebral arteries supply blood to the brain. This complex of arteries forms

a sort of circle—the cerebral arterial circle (Circle of Willis), responsible for

blood supply to the brain.

Most of the deep veins take on names identical to those of the

arteries they customarily parallel. Study Figure 19.18 and note the major

veins. We can pretty much assume that you know the general pattern of

venous return to the heart if you have learned the arteries well. Take note

of the following exceptions: jugulars instead of carotids; inferior and

superior vena cavae instead of aorta; basilic, brachial, and cephalic instead

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of only a brachial; the femoral is fed by the popliteal and supplemented by

the great saphenous. The common iliacs join to form the inferior vena

cava, subclavians become brachiocephalics on each side (there is only one

brachiocephalic artery/trunk), and the superior vena cava is formed from

the joining of the right and left brachiocephalics.

The veins of the head and neck parallel the arteries serving the head

and neck, except for the jugulars noted above. As for venous drainage of

the brain, the internal jugular is fed by cranial venous sinuses (see Figure

19.20). Look at Figure 19.20 to obtain a sense of the distribution of the

cranial venous sinuses seen through the transparent skull. Note that the

cerebral sinuses are made up of the dura mater layer of the meninges.

The azygos system of veins supplements the inferior cava in

draining the anterior body cavity (Figure 19.21). Most of the intercostal

veins drain into the azygos systems. Note that the azygos system assists

the inferior vena cava but empties into the superior vena cava.

The upper extremity is drained by veins that pretty much parallel

the arteries supplying the upper extremity, with the exceptions noted

above. Venous arches drain into radial and ulnar veins, which in turn feed

into the brachial vein. Cephalic and basilic veins are superficial in the arm

and supplement the brachial. You should also note the median cubital vein

in the cubital fossa of the elbow (Figure 19.21). It connects with the basilic

vein medially.

Like the upper extremity, the lower extremity has veins that pretty

much parallel the course taken by arterial supply (Figure 19.26). The

major superficial veins of the lower extremity are the great and small

saphenous veins, which empty into the femoral vein in the thigh and the

popliteal vein at the knee respectively.

Veins of the abdominal cavity (Figure 19.23) are almost identical to

the arterial supply to the different organs (e.g., renal vein drains the

kidney).

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Part of Written Assignment number 7 requires that you trace the

course of red blood cells (RBC) from one location to another. It would be

impossible for me to review all of the possible routes of circulation with

you. Therefore, instead of reviewing particular circulation patterns, I will

give you the following rules to follow:

1. Whenever you route an RBC from venous to arterial, the RBC must

pass through the heart.

2. Try to learn the major blood vessels before you attempt to trace an

RBC.

3. Veins move blood toward the heart; arteries move blood away from

the heart.

4. Many times the name of the "tube" (blood vessel) changes with a

change in location, but it still is the same "tube."

A significant variation in the venous system in the anterior body

cavity is the hepatic portal system (Figures 19.24, 19.25). The hepatic

portal system is a series of veins that coalesce to form the hepatic portal

vein (its two main tributaries are the splenic and the superior mesenteric

vein, though several other veins also contribute). Ultimately, venous blood

from the stomach, pancreas, and small and large intestine reaches the liver

for the purposes of filtration and processing of the nutrient rich blood

from the digestive system. The blood is eventually returned to general

venous circulation through the hepatic veins on the posterior surface of

the liver emptying into the inferior vena cava.

The lymphatic system's main task is to drain excess fluid from

tissue spaces. The lymphatic system then transports this fluid, called

lymph, back toward the heart through lymphatic vessels. To do this job,

the lymphatic system includes the following components: lymph, lymph

vessels, lymph nodes, and the spleen, tonsils, and thymus gland.

Besides its role in returning the fluid lymph to the venous system,

near the heart (we will talk about the general plan of lymph circulation

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below), the lymphatic system also plays a major role in the body's immune

defense system by producing some white blood cells (lymphocytes) and

antibodies. The lymphatic system also transports fats from the digestive

tract to the blood and returns blood proteins back to the vascular system.

The lymphatic system begins as a series of lymph capillaries that

are more permeable than capillaries of the vascular system (Figure

20.2). This stands to reason because a major task of the lymphatic system

is to absorb excess intercellular fluid. Once the intercellular fluid enters

the lymph capillary, it is called lymph.

Lymph capillaries begin to aggregate and form larger vessels called

lymphatics (lymphatic collecting vessels). Lymphatic collecting vessels are

comparable to veins, but differ from them in that they have more valves,

thinner walls, and pass through lymph nodes. Lymphatic collecting vessels

generally follow blood vessels and converge on two major channels (the

thoracic duct and the right lymphatic duct) that return the lymph to the

bloodstream (Figure 20.3).

The thoracic duct drains all but the right extremity, thorax, and

head (Figure 20.3), which is drained by the right lymphatic duct. The

cisterna chyli lies in the abdomen near the origin of the thoracic duct. It

collects lymph from the lower extremities and drains into the thoracic

duct. The thoracic duct and right lymphatic duct return lymph to the blood

stream by emptying at the junctions of subclavian and internal jugular

veins.

Lymph nodes resemble a lima bean in shape. Figure 20.4 shows a

typical lymph node. Nodes are placed throughout the length of the

lymphatic channels (see nodes in Figure 20.3 for examples). Lymph

channels carrying lymph into the node are called afferent lymphatic

vessels and those channeling lymph out of the node are called efferent

lymphatic vessels. As you can observe on our prototypical node (Figure

20.4) the afferent vessels enter the convex surface of the node, whereas the

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efferent vessels exit on the concave side of the node at an indentation

called the hilus. Identify the following structures on the node diagrammed

in Figure 20.4: hilus, capsule, and trabeculae.

Lymphocytes are produced in lymph follicles/nodules of the node

(Figure 20.4). They are the white blood cells that produce the antibodies

which will attack foreign, disease-carrying cells that invade the body.

Phagocytic cells, which ingest and destroy debris and foreign molecules,

are also found in the lymph node. Nodes essentially filter the lymph to

remove any waste products, debris, or foreign substances.

The functional part of a lymph node is called the parenchyma,

found in the medulla and cortex of the node. Figure 20.4 shows the

stroma, the structural part of the node, which includes the capsule and

trabeculae.

The general pattern of lymph circulation (see Figure 20.1) begins in

the spaces between cells, called intercellular spaces. Fluid from the

intercellular space moves into lymphatic capillaries, where it is called

lymph. Lymph capillaries merge to become lymphatics (lymphatic

collecting vessels). The lymph then encounters several nodes. Eventually,

the lymph will find its way to either the thoracic duct or the right

lymphatic duct. These ducts return the lymph into the venous system at

the junction of the internal jugular and subclavian veins.

There are three larger, specialized lymph organs you should locate—

tonsils, spleen, and thymus gland. The tonsils are situated in the posterior

wall of the pharynx (i.e., the throat). They function as large lymph nodes.

The spleen (Figure 20.10) is the largest lymphoid tissue located

posterior to the stomach and under the diaphragm. It is buried deep

within the abdominal cavity. The spleen, however, filters blood, not lymph.

It performs tasks similar to those of a lymph node: ingesting foreign

invaders and worn out materials, producing lymphocytes and the added

task of storing blood (for emergency situations).

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The thymus gland (see Figure 20.10) is located posterior to the

upper section of the sternum, extending somewhat into the lower reaches

of the neck. The thymus helps T-lymphocytes develop.

You should be able to identify areas on the body where clusters of

lymph nodes can be found (see Figure 20.3). The most palpable nodes are

used in clinical assessment and include the following: cervical, axillary,

and inguinal.

There are several clinical applications for you to look up and define.

I encourage you to read over the section on immunity, but I only want you

to be able to define the clinical applications. For instance, AIDS is a virus

that infects and destroys a helper T-lymphocyte, normally responsible for

directing the immune response of other lymphocytes. This leads to an

increasing susceptibility to infections and related disorders. Look up the

clinical terms on your own.

Sample Questions

1. An obstruction in the inferior vena cava would hamper the return of blood from this area. a. head b. neck c. upper extremities d. lower extremities

2. In hepatic portal circulation, blood eventually returns to the inferior

vena cava through these vessels. a. superior mesenteric veins b. portal veins c. renal veins d. hepatic veins

3. Afferent lymphatic vessels enter a lymph node at this site.

a. hilus b. concave side c. convex side d. medulla

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4. The greatest proportion of elastin is found in which type of vessel? a. large arteries b. capillaries c. medium-sized arteries d. veins

5. Lymph is eventually returned here.

a. venous system b. interstitial fluid reservoir c. arterial system d. spleen (for storage)


1. d; 2. d; 3. c; 4. a; 5. a


Instructions



Assignments."

Description


1. Describe the course of a red blood cell from the right brachial vein

to the right ulnar artery.

2. Trace lymph fluid from inguinal lymph nodes to the venous system,

noting important anatomical structures along the way.

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Lesson 20 Respiratory System

Reading Assignment

Read Chapter 21, "Respiratory System." By now you know to use the

objectives to guide your reading (so, why did I tell you, huh?).

Objectives


1. List the functions of the respiratory system. Also, define the three

components of respiration.

2. Identify the anatomical structures of the respiratory system (Figure

21.1). Also, name the bones in which paranasal sinuses are found.

3. Identify the following structures of the larynx (Figure 21.3b, 21.5):

thyroid cartilage, cricoid cartilage, glottis, epiglottis, hyoid bone

and trachea.

4. Describe the structure of an alveolus (Figure 21.3b and 21.10).

5. Identify the lobes, fissures, hilus, "root," and cardiac notch of the

right and left lungs (Figure 21.13). Also, distinguish the left from the

right lung. Identify and describe the pleurae. Summarize tissue

changes in the respiratory system from nasal cavity to alveoli.

6. Describe the mechanics of breathing and the muscles involved. See

Figure 21.16.

7. Identify structures involved in the nervous control of breathing

(ventilation) (Figures 21.17, 21.18).

8. Clinical applications, define each of the following: cystic fibrosis,

pneumothorax, lung cancer, RDS, asthma, and emphysema.

Discussion

The organs of the respiratory system are diagrammed in Figure

21.1. They include the nasal cavity, pharynx, larynx, trachea, bronchi, and

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lungs. Like most of the internal body systems (like the digestive, vascular,

urinary), the respiratory system is largely a network of tubes running to

and from organs pivotal in maintaining the integrity of the system, in this

case—the lungs. The difference between the respiratory system and other

tube networks is that it transports gases rather than solids or fluids.

As your books states, respiration consists of three related functions:

ventilation, external respiration, and internal respiration. External

respiration consists of gas exchange between the external environment

and the red blood cells within the capillaries of the lungs. Internal

respiration has more to do with the distribution of gases, the exchange of

gases between the vascular system and the tissues it supplies. Ventilation

is synonymous with breathing.

But the respiratory system is involved in other functions. These

include voice production and protective reflexes. The respiratory system

adds "character" to sound and makes it into language. The respiratory

system also has some built-in reflexes that protect it—the forceful

expulsion of air in a sneeze represents the respiratory system's effort to

dislodge dust and debris from the nasal cavity or upper reaches of the

respiratory system.

The respiratory system also includes the paranasal sinuses. These

cavities in the frontal, ethmoid, sphenoid, and maxillary bones reduce the

weight of the skull. The sinuses function to moisten and filter inspired air.

The diagram of the upper portions of the respiratory system is

important (Figure 21.3b). It includes the nasal cavity which descends into

what we might consider the "throat" in lay terms. The throat (pharynx) is

actually composed of several important structures that are involved in

both the respiratory and digestive systems. The respiratory components

include the pharynx, larynx, and trachea. The larynx is actually

represented by the thyroid cartilage and the cricoid cartilage (Figure 21.5).

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The larynx merges inferiorly into the trachea. The trachea is composed of

16 to 20 C-shaped cartilages which are open posteriorly (Figure 21.7).

The inside of the larynx is composed of an opening called the

glottis. The glottis is protected superiorly by a flap of elastic cartilage

called the epiglottis. It allows food to pass over the glottis to the esophagus

without entering the glottis and becoming lodged in the trachea. The

lumen (opening) of the glottis can be increased or decreased in size by

contraction and relaxation of the true vocal cords. These are illustrated in

Figure 21.6 along with the false vocal cords.

Note that the nature of the epithelium changes as one moves from

the nasal cavity inferiorly. While the nasal cavity and nasopharyx are

comprised of pseudostratified epithelium, the oropharynx and

laryngopharynx consist of stratified epithelium. Once in the trachea,

however, the epithelium reverts back to the pseudostratified type.

Structures involved in external respiration are represented in a

respiratory zone (Figure 21.9). The respiratory zone begins with a terminal

bronchiole that becomes progressively smaller (respiratory bronchiole,

alveolar duct, aveolar sac) and ends with individual aveoli.

Gases are exchanged across two membranes, one vascular

(capillary), one respiratory (aveolus). Figure 21.10 displays these two

membranes. You already know that capillaries are made up of a single-

layered, endothelial cell membrane. Alveoli are composed of a wall of

simple squamous epithelium (type I alveolar cells). Type II alveolar cells

(septal cells) produce surfactant, a lubricant important in ventilation.

Phagocytic cells (alveolar macrophages) are also found in the walls of

alveoli and function as phagocytic cells anywhere else—they destroy

foreign material.

The thin walled structure of both the alveolus and the capillary

allow for an easy exchange of gases (oxygen and carbon dioxide) between

the respiratory and vascular systems. Gases diffuse (go from areas of high

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to low concentration) across the alveolar-capillary membrane. Carbon

dioxide diffuses into the lungs, for subsequent expiration, and oxygen

diffuses into the blood stream, for subsequent distribution to body tissues.

The lungs are divided into two or three lobes depending on the right

or left. On the right lung, horizontal and oblique fissures mark off

superior, middle, and inferior lobes. On the left lung, a single oblique

fissure separates superior and inferior lobes (Figure 21.13). The left lung

also is marked on its medial surface with a cardiac notch made by the

heart as it lies in the mediastinum. Also identify the hilus and "root" of

each lung.

Lobes of each lung can be broken down even further into lobules.

Terminal bronchioles are separated into discrete compartments bordered

by (elastic) connective tissue. The respiratory bronchioles (Figure 21.9)

within the lobule continue to divide into smaller units called alveolar

ducts. It is within the latter structure that alveoli arise, the functional units

of gas exchange in the lungs.

The tubes leading to the alveoli become progressively smaller.

Other than knowing the main/primary bronchi, you do not have to know

the names of progressively smaller bronchi. However, you should know

how the tissue composition of the tubes changes as the tubes become

smaller. Besides changes in epithelium noted above, from trachea to

bronchioles, one finds progressively less cartilage (the larynx and trachea

are primarily cartilage) and more smooth muscle (the smooth muscles of

the bronchioles is primarily responsible for constriction and dilation of the

airways).

The lungs dominate the thoracic cavity, except for the mediastinum.

Each lung is contained within a double-walled protective sac, called the

pleura. The outer layer is the parietal pleura and the inner layer is the

visceral pleura. The space between the visceral pleura and the parietal

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pleura is called the pleural cavity. The pleural cavity contains a thin layer

of fluid to reduce friction between the two layers of pleurae (Figure 21.11).

Breathing is the mechanical part of respiration involving taking air

into the lungs and then expiring it. It is properly called pulmonary

ventilation (Figure 21.16) and can be broken into two parts: inspiration

and expiration.

Inspiration is an active process involving the expenditure of energy

and the use of several muscle groups. Inspiration is accomplished by

creating a favorable pressure gradient for air to flow into the lungs. This is

done by making the pressure inside the thoracic cavity less than that of the

air outside of the lungs. To make the pressure inside the thoracic cavity

less, the thoracic cavity must be enlarged, and this is accomplished by

increasing the superior-posterior dimensions of the cavity (by contraction

of the diaphragm) and increasing the anterior-posterior dimensions of the

thoracic cavity (by contraction of the external intercostals). The scalene

muscles and the sternocleidomastoid also assist in respiration during

stressful activity or forced inspiration.

Expiration is a more passive process, primarily attributable to the

recoil of the elastic tissue within the stroma of the lungs and the relaxation

of the muscles responsible for inspiration. Forceful expiration is

accomplished by the contraction of the abdominal muscles and the

internal intercostals.

Having already covered the brain, you can probably guess that

nervous control of respiration is controlled by a "center" in the medulla

oblongata of the brainstem. As it turns out, the medullary rhythmicity area

sets the basic respiratory rate. However, several other neurological

structures are involved too. Pneumotaxic and apneustic areas in the pons

help coordinate or modify the relationship between inspiration and

expiration. Finally, we all know from experience that we voluntarily

modify our breathing patterns (holding breath, forcible expiration, etc.).

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Hence, the cerebral cortex is also involved in neurological control of

respiration.

Chemoreceptors in the carotid and aortic bodies send sensory

information to respiratory centers in the brainstem via the

glossopharyngial and vagus nerves (see Figures 21.17 and 21.18). This

allows for moment-to-moment correction of ventilation and respiration.

On your own, look up the clinical applications in objective number

8. You should be able to define each term.

Sample Questions

1. This name is given to the exchange of gases between the lungs and blood. a. inspiration b. expiration c. internal respiration d. external respiration

2. What is the total number of lobes in both lungs?

a. 6 b. 5 c. 4 d. 2

3. Which of the following is not a part of the respiratory system?

a. nose b. eustachian/auditory tube c. pharynx d. larynx

4. Which of the following would not be found in an alveolus of the lung?

a. macrophages b. simple epithelium c. Type II aveolar cells d. plasma cells

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5. Which of the following areas of the brain helps control respiration? a. cerebellum b. hypothalamus c. midbrain d. pons


1. d; 2. b; 3. b; 4. d; 5. d

Go on to Lesson 21.

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Lesson 21 Digestive System

Reading Assignment

Read Chapter 22 in your textbook.

Objectives

1. Name the primary functions of the digestive system. Identify the

major organs and tubes associated with digestion (Figure 22.1).

2. Identify and define the peritoneum, mesentery, mesocolon,

falciform ligament, lesser omentum, and greater omentum (Figure

22.10).

3. Describe the general histology (Figure 22.5) of the GI tract: mucosa,

submucosa, muscularis, and serosa.

4. Identify the structures of the upper part of the digestive system

(Figure 22.12): oral cavity, tongue, palate, oropharynxs, and

esophagus. Also name and identify the three major salivary glands

(Figure 22.16).

5. Describe internal and external anatomy of the stomach and its

major functions (Figure 22.18).

6. Identify the different parts of the small (Figures 22.1 and 22.21) and

large intestines (Figures 22.1 and 22.22). State the primary

functions of the small and large intestines.

7. Identify and locate the organs of the digestive system and accessory

organs of digestion: liver, gallbladder, pancreas (Figures 22.26,

22.20). Generally describe the digestive functions of the liver,

gallbladder, and pancreas.

Discussion

The obvious functions of the digestive system all relate to activities

designed to facilitate the absorption of nutrients, water, and trace minerals

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through the lining of the digestive tract, especially the small and large

intestines. Digestion actually refers to the mechanical and chemical

breakdown of food, which is a pre-requisite to absorption.

The major organs of the digestive system are illustrated in Figure

22.1. I will be summarizing the major anatomical and functional features

of each of the organs and tubes in Figure 22.1 throughout this lesson.

We have already observed that the heart and lungs are enveloped in

protective layers of epithelial and connective tissue. The same holds for

some of the components of the digestive system. The general term used to

refer to these protective and stabilizing membranes is peritoneum. The

parietal peritoneum lines the inner surfaces of the abdominal cavity and

the visceral peritoneum actually touches the organ/structure (Figure

22.9).

The peritoneum can be further divided into sub-units depending on

placement and organ it is associated with. As the parietal peritoneum

extends anteriorly from the dorsal wall of the abdomen, it forms a double-

layered membrane which envelopes most of the organs of the abdominal

cavity. Depending on the organ, the double-layered membrane of

peritoneum may suspend the organ from the posterior wall of the

abdomino-pelvic cavity (see Figure 22.9). If it suspends the small

intestine, then it is called the mesentery. If it suspends a part of the large

intestine, then it is called the mesocolon (Figure 22.10). In sum, the

mesentery and the mesocolon serve to suspend the intestines from the

posterior abdominal wall, leaving the intestines enough latitude for

movement, but keeping them stabilized through attachment to the

posterior abdominal wall.

Several other parts of the double-layered part of the peritoneum are

also illustrated in Figure 22.10. These structures include: the falciform

ligament, which supports the liver anteriorly, the lesser omentum, which

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suspends the stomach from the liver, and the greater omentum, which

loosely attaches the lower portion of the stomach to the transverse colon.

The peritoneal covering continues around the organs of the

digestive system, where it is known as the visceral peritoneum (Figure

22.9). This is in keeping with the convention we have observed for the

heart and the lungs already (e.g., the visceral pleura covers the lungs).

A typical cross-section through the digestive tract reveals that it is a

multi-layered organ with specialized tissues at each layer (Figure 22.5).

The innermost layer is called the mucosa. It is composed of epithelium, as

you probably guessed. It is the portion of the digestive tract responsible for

absorptive functions. The mucosa also contains a thin layer of smooth

muscle called the muscularis mucosa. (Do not confuse this with the

muscularis layer described below. This thin layer of smooth muscle is

actually included in the mucosa layer.)

The second layer is called the submucosa (see Figure 22.5); it is

composed of loose connective tissue which is highly vascular. The

submucosa is very important to the process of absorption of nutrients, as it

contains many blood vessels and lymphatic channels which pass close to

the surface of the lumen of the digestive tract.

The third layer of the digestive tract is the muscularis layer (see

Figure 22.5). It is specialized to churn and mix food. It may also contract

in a manner that will move food further down the digestive tract

(segmentation, peristalsis).

The fourth layer of the typical segment of the digestive tract is

known as the serosa (see Figure 22.5). It is a membrane of epithelial cells

covering loose connective tissue.

In the superior reaches of the digestive system one can observe

several structures in common with the respiratory system (Figure 22.12).

The two systems share a common passageway for a brief period, the

portion of the pharynx posterior to the oral cavity. The mouth, tongue, and

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the palate are included in the digestive system but not the respiratory

because air enters through the nasal cavity, superior to the palate. The

respiratory and digestive systems diverge from one another at the inferior

portion of the pharynx, where the larynx is positioned anteriorly and the

esophagus is positioned posteriorly. As previously mentioned in the

respiratory lesson, the epiglottis covers over the glottis (the opening to the

larynx) so that food may pass over the air passage instead of being inspired

into the trachea or lungs.

You should study Figure 22.16 next. Identify the three major

salivary glands and the general location of each. The salivary glands

secrete digestive enzymes to initiate the process of breaking down the

food.

After food passes down the esophagus it enters the stomach (Figure

22.18). It is here that the digestive process continues in earnest, although

little in the way of absorption occurs in the stomach. Instead, the stomach

secretes a number of digestive enzymes, (e.g., pepsin) that transform the

food into a state more suitable to absorption. By the time the food has

been processed by the stomach it is called chyme. Make certain to identify

by landmarks on the internal and external stomach

The stomach is a J-shaped organ. The concave portion is called the

lesser curvature and the convex inferior part of the "J" is the greater

curvature. These represent the attachments of lesser and greater omentum

respectively. The most superior part of the stomach is called the fundus,

while the superior part in the area of the esophagus is called the cardia.

The area of the stomach near the first part of the small intestines is known

as the pylorus. Note, the folded inner surface of the stomach known as the

rugae.

The majority of nutrient and water absorption is the job of the small

and large intestines. The small intestine absorbs most of the food, and the

large intestine absorbs most of the water and minerals.

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The small intestine is composed of the three parts (Figure 22.1). In

order from the stomach to the large intestine, one would encounter the

duodenum (the first ten inches), the jejunum (the next three feet), and the

ileum (the remaining six-seven feet). The ileum ends at the ileocecal valve

which leads into the cecum of the large intestine. Together, the three parts

of the small intestine receive digestive secretions from the liver, pancreas,

and gall bladder, continue the breakdown of the chyme, and absorb

nutrients.

The large intestine or colon (Figure 22.22) consists of several parts

as well. The large intestine begins as the cecum, a pouch at the inferior

extent of the ascending colon. This is a short segment of the large

intestine; the appendix is a blind pouch that is suspended form the cecum.

Absorption of nutrients ends in the small intestines, but the large

intestines still has the important job of absorbing water and minerals.

Extending in a superior direction from the cecum is the ascending

colon. It turns medially at the hepatic flexure and becomes the transverse

colon. The transverse colon runs across the anterior body wall and then

turns inferiorly at the splenic flexure to become the descending colon.

From this point the colon ends in three short segments: a short sigmoid

colon, the rectum, and the anal canal (Figure 22.22).

Other features to note on Figure 22.22 include the haustra,

dilations in the large intestine throughout its course. The haustra are

periodic dilations where the contents of the large intestine pause for

further mixing and absorption of water and minerals. The large intestine is

also covered with a longitudinal muscle throughout its entire length called

the taeniae coli. The taeniae coli are capable of strong peristaltic

contractions that move the contents of the large intestine along toward the

rectum for defecation.

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Assisting in the digestion and absorption of food are three accessory

organs: the liver, gall bladder, and pancreas. All three secrete enzymes that

assist in digestion.

The liver is situated in the superior right portion of the abdominal

cavity (Figures 22.21, 22.26), just inferior to the diaphragm. The liver has

four lobes; left, right, caudate, and quadrate. The latter two are seen only

on an inferior view. The liver is attached to the anterior body wall by the

falciform ligament.

From our earlier discussion of hepatic portal circulation you know

that the liver plays an important role in the filtration of blood from the

intestines. Indeed, important functions of the liver include the removal of

old erythrocytes, filtration of bacteria and toxins, and storage of glucose in

the form of glycogen.

From the point of view of digestion, however, the essential function

of the liver is production of bile. Bile is needed in the breakdown and

absorption of fats in the digestive tract. The liver produces bile that is

stored in the gall bladder (Figure 22.26). When bile is to be secreted into

the duodenum, the gall bladder secretes bile into the cystic duct and the

liver secretes bile into the common hepatic duct. These two structures join

to form the common bile duct to the duodenum (Figure 22.20).

The last of the accessory digestive organs is the pancreas (see

Figure 22.20). You may recall that the pancreas is an endocrine gland. In

fact, it has both endocrine and exocrine functions. The latter are

associated with the digestive system. Like the liver and the gall bladder,

the pancreas has a duct that leads to the first part of the small intestine

(Figure 22.20). The pancreas secretes pancreatic juice into the pancreatic

duct. The pancreatic duct joins with the common bile duct at the

duodenum to form the hepatopancreatic ampulla (Figure 22.20). The

pancreatic juice contains enzymes that assist in the digestion of

carbohydrates, fats, and proteins.

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Sample Questions

1. Name the portion of the peritoneum that suspends parts of the large intestines from the posterior wall of the abdominal cavity. a. mesocolon b. mesentery c. lesser omentum d. retroperitoneum

2. This part of the small intestine would be cut first if surgery was being

performed to remove an obstruction from the duodenum. a. mucosa b. muscularis c. serosa d. submucosa

3. This part of the digestive system is shared with the respiratory system.

a. larynx b. pharynx c. palate d. submandibular gland

4. This structure is the first that would be encountered by a button

swallowed by a child after the button passed through the ileum. a. cecum b. hepatic flexure c. ascending colon d. jejunum

5. The lesser omentum connects the liver to which of the structures listed

below? a. stomach b. pancreas c. spleen d. gall bladder


1. a; 2. c; 3. b; 4. a; 5. a

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Instructions



Assignments."

Description


1. Trace a button swallowed by a child through the digestive system,

noting anatomical structures it would pass through from oral cavity

to anus.

2. Three major accessory digestive organs contribute digestive

enzymes to the process by way of the hepatopancreatic ampulla.

Identify the three organs and their enzymes. Also explain how

enzymes from each organ reach the hepatopancreatic ampulla.

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Lesson 22 Urinary System

Reading Assignment

Read Chapter 23 on the urinary system. Pay attention to the

objectives for the lesson.

Objectives

1. Identify the organs of the urinary system (Figure 23.1). Also, state

the functions of the urinary system.

2. Describe the external (location, hilus) and internal anatomy of the

kidneys: cortex, medulla, renal pyramids, minor calyx, major calyx,

and renal pelvis (Figure 23.3).

3. Define the microscopic anatomy of a nephron: glomerulus,

glomerular capsule, tubules, loop of Henle, vasa reta, peritubular

capillaries, collecting tubule, and papillary duct (Figures 23.4 and

23.5).

4. Describe the basic functions of each part of a nephron: filtration,

reabsorption, secretion.

5. Name the tissue layers of the ureters and the urinary bladder, (also

identify detrusor muscle, rugae).

6. Identify the urethra (and sphinctors) and the bladder trigone

(Figure 23.16).

7. Describe the normal micturation and identify the nervous control of

micturation: visceral afferent neurons, micturation center (pons),

parasympathetic, sympathetic, and somatic pathways (see Figure

23.17).

8. Trace a voided molecule of water from kidney to urethra.

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Discussion

Like the digestive and respiratory systems earlier, the urinary

system is a network of tubes connecting various organs. It also transports

fluid like the vascular system. But as you can see by Figure 23.1 the urinary

system is a lot more simple and quite a bit shorter than the digestive

system.

The kidneys drain into two tubes on either side of the abdominal

cavity. These tubes are called ureters. The ureters drain into the urinary

bladder, which in turn drains urine into the urethra to be voided from the

body. The components of the urinary system are identified in Figure 23.1.

The primary functions of the urinary system are to filter blood for

toxins and waste products, and to secrete excess water. The kidneys help

maintain the balance of electrolytes and the amount of water in the body

at suitable levels.

The kidneys are located against the posterior abdominal wall

between T12 and L3 vertebrae and the beginning of the lumbar vertebrae.

They are also retroperitoneal (posterior to the peritoneal membranes).

Normally, people have two kidneys, but it is not unusual to have only one

kidney.

Though larger, the kidneys are shaped similar to the lymph nodes,

somewhat like a lima bean. The concave surface has a hilus, like the lymph

node. Similarities end there, however, because the kidneys are responsible

for filtering blood not lymph.

Figure 23.3 reveals the gross appearance of the kidney. It has a

peripherally located cortex surrounding an inner medullary area. Tubes

are plentiful throughout. The minor calyces then unite to form the major

calyx. Major calyces converge at the renal pelvis and hilus of each kidney.

Ureters begin at the hilus of each kidney.

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The histology of the kidney is represented by the basic functional

unit called the nephron. A nephron is illustrated in Figures 23.4, 23.5, and

23.9. A network of capillaries, the glomerulus (Figure 23.6), filters blood

and permits the filtrate of water and waste products to enter the proximal

part of the nephron. Most of the water is reabsorbed from the nephron's

tubules back into the vascular system through capillaries surrounding the

tubules of the nephron (Figure 23.9).

The tubule leading from the nephron does not lead directly to the

collecting duct of the nephron, but rather the tubule is tortuous (winding)

and include a lengthy, convoluted section proximally, a nephron loop, and

a lengthy, distal convoluted tubule (Figure 23.5). From the collecting duct

of each individual nephron, the urine passes into the medulla of the kidney

where it is received by the minor calyx (when it can be properly called

urine) and then on to the major calyx and into the ureter.

The nephron works through three processes—filtration,

reabsorption, and secretion. Filtration occurs at the glomerulus, while

reabsorption and secretion occur in the tubules.

The ureter and the bladder are similar to the other tube systems

inside the body in the sense that each is comprised of several layers of

tissue. The general theme of the tubes within the body has been epithelium

on the inside, smooth muscle in the middle, and connective tissue on the

outside.

The ureter has an inner layer of mucosa which is comprised of

transitional epithelium. Transitional epithelium allows for considerable

distension. A middle smooth muscle layer called muscularis is likewise

found lining the ureters. Finally, an outer layer of fibrous connective

tissue, called the adventitia, completes the walls of the ureters.

The urinary bladder (see Figure 23.16) is similarly organized, with a

layer of transitional epithelium lining the inside of the bladder to permit

distention with the accumulation of urine. The second layer of the bladder

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is the smooth muscle layer, again called the muscularis (also known as the

bladder detrusor muscle). Finally, the most superficial layer of the bladder

is a continuation of the peritoneum called the adventitia.

The inferior opening in the bladder is called the urethra. It is in

close proximity to the openings of each ureter into the bladder and forms a

triangle (Figure 23.16). This area is known as the bladder trigone. Once the

urine has entered the urethra, it must pass internal and extrenal

sphincters to be expelled.

Micturation (urination) is a complex activity (see Figure 23.17) that

is part involuntary and part voluntary. Sympathetic innervation of the

smooth muscle (detrusor muscle) of the urinary bladder allows for filling.

As the bladder fills with urine, stretch receptors in the detrusor muscle of

the bladder are stimulated. This information is feedback to the spinal cord

and then upward to micturation center in the pons. The micturation center

in the pons then causes parasympathetic fibers to stimulate contraction of

the detursor muscle and relaxation of the internal sphinctor. The

micturation center inhibits somatic motor neurons innervating the

external sphinctor. Finally, sympathetic innervation of the bladder is

inhibited to allow for contraction. The cerebrum may also delay urination

for a time by somatic motor stimulation of the external sphinctor.

I will leave you to your own devices to satisfy the final objective of

tracing a water molecule from the kidney to the urethra. Make certain to

detail the pathway followed by the water as it negotiates the complexities

of the nephron. Refer to Figures 23.1, 23.3, 23.5, 23.14 and 23.16 to

develop a complete answer.

Sample Questions

1. Blood is filtered by this structure in the nephron. a. proximal convoluted tubule b. loop of Henle c. glomerulus

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d. collecting duct

2. Name the tube that leads from the kidney to the bladder. a. ureter b. collecting duct c. convoluted tubule d. minor calyx

3. Which of the following is not a component of the urinary system?

a. bladder b. prostate gland c. urethra d. ureter

4. Urine passing through the ureter is in direct contact with which tunic

layer? a. muscularis b. mucosa c. submucosa d. serosa

5. As a water molecule leaves the collecting duct of the nephron, it next

enters this structure. a. ureter b. urethra c. bladder d. minor calyx


1. c; 2. a; 3. b; 4. b; 5. d

Go on to Lesson 23.

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Lesson 23 Reproductive System

Reading Assignment

Read Chapter 24 in the textbook. Use the objectives below to guide

your reading.

Objectives

1. List the functions of the reproductive system.

2. Identify and describe structures of the male reproductive system

(Figures 24.1, 24.3): seminiferous tubules, epididymis, ductus (vas)

deferens (and ampulla), seminal vesicle, ejaculatory duct, prostate

gland, bulbourethral gland, urethra, penis.

3. Identify and describe structures of the female reproductive system

(Figures 24.11 and 24.12): ovaries, uterine (fallopian) tube, uterus

(fundus, body, cervix), vagina.

4. Describe the structure and position of the uterus (Figure 24.11).

5. Describe the path taken by a sperm cell from the testes to the

urethra (Figures 24.1, 24.8).

6. Describe the placenta, its anatomy, and the process of exchange

that occurs there (Figure 24.24). Identify substances that may cross

the placenta to the fetus during gestation. Define the terms chorion,

chorionic villi, and decidua basalis.

7. Define the following clinical applications: ovarian cancer, breast

cancer, prostate cancer, testicular cancer.

Discussion

The rather obvious function of the reproductive system is

procreation. Union of a sperm cell and an egg cell is called fertilization and

results in the formation of the zygote, a fertilized egg. The zygote

differentiates as it travels medially down the uterine tube toward the

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uterus for eventual implantation and gestation. (Consult Lesson 2,

"Embryology," and Chapter 3 for a review of the development of the zygote

and its derivatives.) The sex glands accomplish this task through the

production of gametes (sex cells, sperm cells and egg cells).

Besides the rather obvious function, the reproductive systems exert

a significant influence on the development and maintenance of some

tissues—mostly the placement of hair, structure of the larynx, relative

amount of muscle mass, weight of bones, and other features that

distinguish men and women. This is accomplished through the secretion

of sex hormones, testosterone in the male, estrogen and progesterone in

the female. Furthermore, the adequate secretion of sex hormones from the

gonads (sex glands) serves to promote the development of gametes (sex

cells).

Figure 24.1 displays the majority of the structures of the male

reproductive system. This system begins with the structure in the testes

responsible for production of sperm cells, the seminiferous tubules.

Hence, the seminiferous tubules are the functional structures within the

testes. The testes are situated external to the body wall in a sack known as

the scrotum. The scrotum can constrict to bring the testes closer to the

body for warmth. But normally the testes are suspended in the relaxed

scrotum because sperm requires a somewhat lower temperature than core

body temperature to be produced. Sperm should not be confused with the

fluid it is suspended in, semen. Semen is produced by separate structures

in the male reproductive system (see below).

A structure closely associated with a testis is the epididymis,

positioned on the posterior surface of a testis. The epididymis functions to

store and nourish immature sperm cells deposited there from the

seminiferous tubules (see Figure 24.1).

The ductus deferens is a long tube leading from the epididymis to

the ejaculatory duct (see Figure 24.1). The ductus deferens takes a long

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and tortuous route, at one point arching over the urinary bladder and

ureter before coursing posterior to the urinary bladder. The transition

from the ductus deferens to the ejaculatory duct is signaled by its merger

with a duct from the seminal vesicle.

After transporting the sperm to the vicinity of the seminal vesicle

(Figure 24.1) the ductus deferens joins a short duct from the seminal

vesicle to form the ejaculatory duct. It is at this point that some semen is

added to the sperm from the seminal vesicle. The seminal vesicle

contributes about 60 percent of the total volume of semen.

Most of the remaining semen is added by the very next accessory

gland, the prostate gland (see Figures 24.1 and 24.8). Semen from the

prostate gland is added as the ejaculatory duct passes through the gland

and joins the male urethra.

Figure 24.8 also illustrates the bulbourethral glands. The glands are

responsible for producing a viscous lubricant for the urethra at the time of

coitus. Note that the secretions of the bulbourethral glands are not part of

the semen.

The final part of the trip for the sperm cell suspended in the semen

is through a tube the reproductive system shares with the urinary system—

the urethra. The sympathetic and parasympathetic divisions of the ANS

cooperate to stimulate different aspects of the sexual excitation and the

outcome of coitus for the male—ejaculation.

The female reproductive system includes the ovaries, uterine tube,

uterus (womb), and the vagina. These structures are pictured in Figure

24.10. Although the female reproductive system's physiology is

complicated compared to that of the male, its anatomy is rather

straightforward.

The ovaries are situated laterally against the inside margin of the

pelvis, the iliac fossa (Figure 24.12). The ovary on each side is the

equivalent of the testes in the male and is responsible for the production of

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the female reproductive cell, the egg cell. The female is born with all the

egg cells she will ever have. The egg cells are not produced anew with each

cycle, but rather dormant/immature cells mature and are released in a

predetermined order. Once the activated egg cell is ready, it is released by

the ovary—the act of ovulation.

Once the egg cell has ovulated it travels, surprisingly, into the

peritoneal cavity in the vicinity of the ovary. It is the job of the uterine tube

and its appendages (the fimbrae) to capture the egg cell from the

peritoneal cavity and help it begin its trip medially toward the uterus.

Normally, union of the sperm cell and egg cell (fertilization) occurs in the

distal 1/3rd of the uterine tube. The zygote then travels toward the uterus

while experiencing rapid cell division to form a ball of cells referred to as a

morula (see Lesson 2 on Embryology).

Once the morula enters the centrally positioned uterus, it

differentiates into a structure called a blastocyst. This is the structure that

implants itself into the inner layer of the uterus (see Figure 24.12), the

endometrium. The endometrium of the uterus is an optimal environment

in which the blastocyst may thrive, developing and differentiating into the

embryo and then the fetus. The gross appearance of the uterus is that of an

upside-down triangle, with its apex pointing in an inferior direction. The

inferior neck-like region of the uterus is called the cervix. The cervix is a

vital landmark during the birth process. Much of the labor during the birth

process amounts to dilation of the cervix to the size of 10 centimeters so

that the infant's head can pass through the birth canal. The superior, top

region of the uterus is known as the fundus (note the fundus of the

stomach in comparison). The lateral sides of the uterus make up most of

the body of the organ.

The birth canal is the vagina (see Figure 24.12). The vagina serves

as the female sex organ during coitus and the birth canal during delivery of

the infant. At the time of birth, the infant is moved (head first in a normal

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delivery) down the birth canal after it separates from the wall of the

uterus.

In addition to the delivery of the infant, a second structure is

delivered at the time of birth, a temporary organ called the placenta (see

Figure 24.24). The placenta is made up of both fetal and maternal

contributions. The fetal contribution is known as the chorion. The chorion

is comprised of mesoderm cells and a part of the support tissues of the

blastocyst, the trophoblast. The maternal contribution is part of the wall of

the uterine wall (endometrium), the deciduas basalis.

Extensions/projections from the chorion penetrate into the endometrium

to bring fetal blood vessels into close proximity with maternal blood; these

projections of the chorion are known as the chorionic villi.

In a normal pregnancy, fetal and maternal blood do not mix within

the placenta. Rather, fetal blood percolates through capillaries in close

proximity to maternal blood (see Figure 24.24), close enough for the

exchange of oxygen and nutrients for carbon dioxide and waste products

between the mom and the fetus. Unfortunately, other harmful products

may also cross at the placenta, nicotine, alcohol and other drugs, and

viruses. Hence, it is very important that the pregnant woman avoid

substances that would be harmful to the growing infant and monitor diet

and exercise carefully. She is literally eating, drinking, and breathing for

the infant in the womb.

The final pages of Chapter 24 provide a description of each of the

clinical conditions mentioned in the final objective for this lesson. Refer to

those pages and look up each of the cancers listed in objective number 7.

Sample Questions

1. Name the structure in the female reproductive system located posterior and superior to the urinary bladder. a. uterine tube b. uterus

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c. deciduas d. vagina

2. This is a structure that helps form the placenta.

a. cervix b. deciduas basalis c. fundus d. rugae

3. This structure of the male reproductive system is responsible for

temporary storage of sperm cells until they reach maturity. a. epidiymis b. seminiferous tubules c. prostate gland d. bulbourethral gland

4. In the male, this tube is shared by the urinary system and the

reproductive system. a. ureter b. prostate gland c. urethra d. ductus deferens

5. These finger-like projections penetrate the endometrium of the uterus

to bring fetal blood close to maternal blood. a. ciliated tubules b. decidua capsularis c. pseudo-stratified epithelia d. chorionic villi


1. b; 2. b; 3. a; 4. c; 5. d

Examination #4 (FINAL)

The final examination follows Lesson 23. This will be a one-hour,

supervised examination in which no books, notes, or other aids may be

brought to the exam. The final consists of forty multiple-choice questions.





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Anatomy Study Guide