Animal Histology by Sir Mario S. Torres

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ANIMAL HISTOLOGY

Background The tissues of multicellular animals are organized on the basis of the type of cells which form the tissues,thus the cells composing the tissues are specialized (Campbell et al., 2000; Raven and Johnson, 1999). Eachtissue has a common structure and function and ischaracteristically held together by intracellular materials.It represents specialization of the properties that all

protoplasms possess such as contractility, excretion and irritability.

An animal has four categories of tissues namely:epithelium, connective, muscular and nervous. Theepithelium forms a protective covering; the connectiveserves as binding and supportive tissue; muscular contracts for movement; and the nervous tissue is for conduction of impulse and reception of stimuli (Hickmanet al., 1996).

Tissues interact with their environment, and theconstant changing of their environment demands a

considerable degree of adaptability (Burkitt et al., 1996;Sandritter and Thomas, 1979). Hence, their failure toadapt to changes may result to histopathologic conditionwhich refers to the abnormalities or diseases associated with tissues.

Characterization of animal tissues throughmicroscopic observations of will be performed in thislaboratory activity.

Goals At the end of the activity, the students should beable to:

1. identify the major types of tissues and their subgroups;

2. compare the morphology of the different tissues, and3. categorize each of the tissues based on their

general functions and locations in the body.

ACTIVITY SEVEN



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Laboratory supplies and Materials

compound microscopexylene and cottonprepared slides of tissues:

lung cerebrum striatedstomach adipose cardiackidney tendon smoothtrachea lymph node bloodskin fibrocartilageurinary bladder elastic cartilageesophagus hyaline cartilagespinal cord decalcified bone

Methods

1. Familiarize with the classification of animal tissues.

Figure 7.1 Classification of animal tissues



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2. Characterize the epithelial tissues according to their structural properties and

classification.

Epithelial tissues are formed by closely aggregated cells resembling sheetor membrane. They cover or line surfaces or masses of cells in glands. One

of their surfaces is attached to a basement membrane, while the other is free.They have plenty nerve fibers and are considered avascular because they do nothave blood supply. Their nutrition is through osmosis or diffusion from underlyingvascular connective tissues. They are classified according to cell shape andnumber of cell layers.

Table 7.1a. Classification and descriptions of epithelial tissues

Basis Description

Cell shape

Squamous

Cuboidal

Columnar

The cells are thin, broad and with flat appearance.

The cells are roughly thick than wide, and cube-like.

The cells are tall than wide; and in vertical section, resemblesrectangular-shape. Some are modified with cilia, the hair-likeprojections at the distal ends.

Layering of cells

Simple

Stratified

Pseudo-stratified

Transitional

It is one-cell thick.

It is two or more-cell thick.

It is composed of columnar cells of one-cell thick, however, itlooks like stratified because its cells extend in varied distancesfrom the basement membrane, thus, it gives the false layeredappearance.

It is composed of rounded, or plump cells with the ability to to be

stretched. Hence, the superficial cells are flattened when theorgan is distended and rounded when empty.

Sources: Torres et al., 2004; Campbell et al., 2000; Hickman et al., 1996



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Table 7.1b. Specific examples of epithelial tissues and their location

Specific Type Location

Simple squamous

Simple cuboidal

Simple columnar

Stratified squamous

Pseudostratified ciliated columnar

Pseudostratified non-ciliated columnar

Transitional

lining walls of the blood vessels, bowman’scapsule of the kidneys, alveoli of the lungs,cavities of the heart

thyroid follicles, pigmented retina of the eyes,ducts of glands

mucosa of the stomach,small and large intestines

skin, esophagus, vagina

trachea

fallopian tube, oviduct

urinary bladder, urether, urethra


2.1 Examine the provided prepared slides using the OIO and locate the labeled partson the diagrams.

Simple squamous epithelium



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Stratified squamous epithelium

Simple columnar epithelium

Pseudostratified ciliated columnar epithelium



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Simple cuboidal epithelium

Transitional epithelium

Figure 7.2 Photomicrographs of epithelial tissues, 1000 X

2.2 Answer item in the worksheet.

3. Characterize the connective tissue according to their structural compositionand classification.

Connective tissues are widely separated by huge amount of intercellular or fiber-filled ground substance. The gel-like matrix of the groundsubstance entrench different kinds of cells and protein fibers. They providestructural and metabolic support for other tissues or organs of the body. Hence,they function with a variety support mechanisms such as packing, storage,



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transport, defense and repair. They are classified either as loose connectivetissue or dense connective tissue based on the composition and arrangement of fibers. Some specialized connective tissues are also classified according to their structural composition, as well as their functions. These tissues are outlined inTable 7.2.

Table 7.2. Types and descriptions of connective tissues

Type Description Location

Arrangement of fibers

Loose CT

Dense CT

These are tissues with fibers arranged in ameshwork, and are composed of three main fibersclassified as collagen, elastic and reticular. Thereare two main loose connective tissues:

Loose areolar tissue has a variety of proteinaceous fibers, including collagen andelastin.

Reticular tissue is a type of loose irregular CT andhas a network of reticular fibers. It resemblesareolar CT, but the only fibers in its matrix arereticular fibers, which form a delicate networkalong with fibroblasts.

These are composed primarily of collagenousfibers which are arranged parallel to each other.They are resistant to stretching and are further grouped into.

Dense regular are composed of collagen fiberswhich appear silvery white. They are arranged inan orderly parallel manner conferring their greatstrength and toughness yet somewhat pliable.

Dense Irregular contain collagen fibers that areirregularly interwoven. They are found in parts of the body where tensions are exerted in variousdirections.

lymph nodes, liver andbone marrow

spleen; lymphatic system

tendons, ligaments.

dermis of the skin, jointcapsules, heart valvesand, membrane (fibrous)capsules around thekidney, liver, testes andlymph nodes

Structural composition

Cartilage This is a semi rigid form of connective tissue withclosely packed fibers embedded in a gel-likeground substance or matrix. Cells within smallpockets, called lacunae, are also present.

Hyaline is an avascular cartilagenous tissue witha translucent ground substance which is madepredominantly of collagen and is avascular.

bones, joints; embryonicskeleton



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Osseous

Vascular

Adipose

Elastic is similar to hyaline but contains elasticbundles (elastin) scattered throughout the matrix.

Fibrocartilage is a specialized typeof cartilagefound in the areas requiring tough support or great

tensile strength.

This is a rigid form of connective tissue consists of cells fibers and ground substance or matrix whichis calcified.

This is a fluid tissue consisting of free cells andfliud intercellular plasma. The cells are further classified as red blood cells (erythrocytes) andwhile blood cells (leukocytes)

This tissue comprises the bulk of body fat. It hasa high percentage of fat cells which form groupsof masses or fat lobules separated by partitions of fibrous septa.

pinna of the ear, walls of the auditory (Eustachian)tubes, larynx andepiglottis

between intervertebraldiscs, pubic and other

symphyses, connectingtendons or ligaments tobones.

skeleton of higher vertebrates

vascular system;lymphatics

subcutaneous tissue


3.1 Examine the provided prepared slides using the OIO and observe the types of fibers present and their arrangement, and the cells that are found in the matrixof the tissue.

Loose areolar tissue



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Reticular tissue

Adipose tissue

Dense regular tissue



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Dense irregular tissue

Hyaline cartilage tissue

Fibrocartilage tissue



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Elastic cartilage tissue

Osseus tissue

Vascular tissue

Figure 7.3 Photomicrographs of connective tissues, 1000X



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4.. Characterize muscular tissue according to their structural composition andfunction.

Muscular tissue has highly developed the property of contractility, hence, it

produces force and cause motion, either locomotion or movement within internalorgans. Much of muscle contraction occurs without conscious thought(involuntary contraction) and is necessary for survival, while voluntary musclecontraction is used to move the body, and can be finely controlled. Outinedbelow are the types of muscular tissue:

Table 7.3. Muscle tissues and their corresponding descriptions

Type Description Location

Skeletal It is a straited, voluntary muscle which isresponsible to react to conscious control.The muscle fibers are much longer andlarger in diameter than the smooth musclefibers. Each muscle fiber shows distinctcross-striation, and is multinucleated, withthe nuclei situated below the sarcolemma.

attached to the skeleton

Smooth It is a non-straited, involuntary muscle is notunder conscious control. Each muscle fiber is a spindle-shaped cell with an elongated

or ovoid centrally-located nucleus.

walls of organs and structuressuch as the esophagus,stomach,intestines, bronchi,

uterus, urethra, bladder andblood vessels

Cardiac It is a straited, involuntary muscle. It hasslender ovoid or elongated nuclei seen atthe periphery of the fibers.

heart

Sources: Torres et al., 2004; Campbell et al., 2000; Hickman et al., 1996; di Fiore, 1989

4.1 Examine the prepared slides of the muscle tissues using the OIO and notetheir distinguishing characteristics.



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Cardiac muscle tissue

Figure 7.4 Photomicrographs of muscle tissues, 1000X

Smooth muscle tissue

Skeletal muscle tissue



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5. Characterize the nervous tissues according to their structural properties and

cell types.

Nervous tissue is specialized for the reception of stimuli and for the conductionof impulses from one region to another. There are two major cell populations in

the nervous tissues, the neurons and neuroglia. The brain and the spinal cordare composed of tissues of the gray and white matter. In the central nervoussystem, the white matter is formed by the myelinated axons, while theunmyelinated dendrites and cell bodies form the gray matter.

Table 7.4 Nervous tissue cells and their corresponding description and location

Type of neural cells Description Location

Neurogila They are variety of non-nervous cells. Its

named “glia” means glue whichdescribes its basic supportive function.

Scattered throughout the brain

and the spinal cord

Neurons The neurons (nerve cells or neurocytes)are consists of cell body (cyton) with longprocesses (dendrites) which extend up tothe peripheral terminals.

Gray matter of the Centralnervous system; white matter of the brain like the basal ganglia;the cerebrospinal andsympathetic ganglia of theperipheral nerves

Sources: Raven and Johnson, 1999; Tortora and Grabowski, 1996; di Fiore, 1989

5.2 Examine the structure of brain tissue and cells in the prepared slide using theLPO and OIO.

Neuron and Neuroglia, 1000X



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Gray and White matter, 100x

Figure 7.5 Photomicrograph of nervous tissues

6. Answer all items in the worksheet.



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1. Summarize the specific functions of the different epithelial tissues.

Type Specific function

Simple squamous

Stratified squamous

Cuboidal

Simple columnar

Pseudostratified columnar

Transitional

Name DateGroup No. Professor

WORKSHEET SEVEN : ANIMAL HISTOLOGY



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2. Summarize the specific functions of the different connective tissues.


Loose areolar tissue

Reticular tissue

Adipose tissue

Dense regular connective tissue

Dense irregular connectivetissue

Hyaline cartilageTissue

Fibrocartilagetissue

Elastic cartilage

Osseous tissue

Vascular tissue



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3. Give the specific functions of muscular tissues.


Cardiac

Smooth

Skeletal

4. Give the specific functions of the cells of the nervous tissues.

Types of Cell Specific function

Axon

Dendrite

Neuroglia



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Conclusion(s)

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References

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Making Connection

In most tissues, fibrous scar forms a functionally adequate, unspecialized,replacement for damaged tissues provided sufficient normal tissue remains. Withtime, the red appearance of recent scar is gone and cellularity of the scar diminishes and contracts which become virtually undetectable macroscopically.How does epithelial regeneration account to this tissue repair?

Documents

Animal Histology by Sir Mario S. Torres