Chapter 4

Biology 25: Human BiologyProf. Gonsalves

Los Angeles City College

Loosely Based on Mader’s Human Biology,7th edition

I. Life is based on many structural levelsI. Life is based on many structural levels

Levels of animal structure:Levels of animal structure:

Atoms and molecules Atoms and molecules CellsCells TissuesTissues OrgansOrgans Organ systemsOrgan systems OrganismOrganism: May consist of a single cell or a : May consist of a single cell or a

complex multicellular organism.complex multicellular organism.

Levels of Structural Organization in an Animal

TISSUES:TISSUES: Most animal cells are organized into tissues.Most animal cells are organized into tissues.

Cooperative unit of very similar cells that perform Cooperative unit of very similar cells that perform

a specific function. a specific function.

Tissue comes from Latin word meaning “weave”.Tissue comes from Latin word meaning “weave”.

Cells of tissues may be held together by:Cells of tissues may be held together by:

FibersFibers

Glue-like substanceGlue-like substance

Plasma membrane structuresPlasma membrane structures

Tissue structure is related to its function.Tissue structure is related to its function.

TISSUES:TISSUES:There are four main types of animal tissue:There are four main types of animal tissue:

1. Epithelial1. Epithelial

2. Connective2. Connective

3. Muscle3. Muscle

4. Nervous4. Nervous

1. Epithelial Tissue1. Epithelial Tissue Cells are tightly fitted together in continuous Cells are tightly fitted together in continuous

layerslayers or or sheetssheets.. Cover outside of body (skin), line organs and Cover outside of body (skin), line organs and

internal body cavities (Mucous membranes of internal body cavities (Mucous membranes of digestive, respiratory, and reproductive systems).digestive, respiratory, and reproductive systems).

Tight packaging allows tissue to act as a Tight packaging allows tissue to act as a barrierbarrier to protect against mechanical injury, infection, to protect against mechanical injury, infection, and fluid loss.and fluid loss.

Two surfaces:Two surfaces:Free surfaceFree surface: Exposed to air or fluid.: Exposed to air or fluid.Bottom surfaceBottom surface:: Attached to underlying tissues Attached to underlying tissues

by a by a basement membranebasement membrane, a dense layer of , a dense layer of protein and polysaccharides.protein and polysaccharides.

1. Epithelial Tissue1. Epithelial TissueCan be classified based on two criteria:Can be classified based on two criteria:

A. Number of layers:A. Number of layers:SimpleSimple: : One layer.One layer.StratifiedStratified: Several layers: Several layers

B. Shape of cells:B. Shape of cells:SquamousSquamous: Flat cells.: Flat cells.CuboidalCuboidal: Cube shaped cells: Cube shaped cellsColumnar:Columnar: Column shaped cells Column shaped cells

ExampleExample: : Simple squamous epitheliumSimple squamous epitheliumStratified columnar epitheliumStratified columnar epithelium

1. Epithelial Tissue1. Epithelial TissueSome epithelial tissues, such as mucous Some epithelial tissues, such as mucous

membranes, absorb and secrete chemical membranes, absorb and secrete chemical solutions.solutions.

Mucous membranes:Mucous membranes:Digestive tract epithelium (mucous Digestive tract epithelium (mucous

membranes) secretes mucus and membranes) secretes mucus and digestive enzymes.digestive enzymes.

Respiratory tract epithelium secretes Respiratory tract epithelium secretes mucous that helps trap dust particles mucous that helps trap dust particles before they reach the lungs.before they reach the lungs.

Cell Surfaces B. B. Extracellular matrix:Extracellular matrix: Sticky layer of glycoproteins found Sticky layer of glycoproteins found

in in animalanimal cells. cells. Important for attachment, support, protection, and Important for attachment, support, protection, and response to environmental stimuli.response to environmental stimuli.Junctions Between Animal Cells:Junctions Between Animal Cells:

Tight JunctionsTight Junctions: Bind cells tightly, forming a leakproof : Bind cells tightly, forming a leakproof

sheet. Example: Between epithelial cells in stomach sheet. Example: Between epithelial cells in stomach

lining.lining.

Adhesion JunctionsAdhesion Junctions: Rivet cells together, but still allow : Rivet cells together, but still allow

material to pass through spaces between cells.material to pass through spaces between cells.

Gap JunctionsGap Junctions: Allow water and other small molecules : Allow water and other small molecules

to flow between neighboring cells. to flow between neighboring cells.

2. Connective Tissue2. Connective Tissue Relatively few cells surrounded by large amounts Relatively few cells surrounded by large amounts

of nonliving material (of nonliving material (matrixmatrix).). Cells secrete the matrix, which can be solid, Cells secrete the matrix, which can be solid,

liquid, or gelatinous.liquid, or gelatinous. Diverse functions. Mainly bind, support, and Diverse functions. Mainly bind, support, and

connect other tissues.connect other tissues. Six types of connective tissue in humans:Six types of connective tissue in humans:

1. 1. Loose Connective TissueLoose Connective Tissue: Most widespread : Most widespread connective tissue in vertebrates. Loose matrix connective tissue in vertebrates. Loose matrix with fibers, with fibers, packingpacking material. Attaches skin to material. Attaches skin to muscles, binds and holds tissues and organs in muscles, binds and holds tissues and organs in place.place.

2. 2. Adipose (fat):Adipose (fat): Pads and insulates body. Pads and insulates body. Energy storage.Energy storage.

Types of connective tissue in humans (Continued):Types of connective tissue in humans (Continued):

C. C. BloodBlood: Fluid matrix (: Fluid matrix (plasmaplasma) has water, salts, and ) has water, salts, and proteins. Red and white blood cells.proteins. Red and white blood cells.

D. D. Fibrous Connective TissueFibrous Connective Tissue: Matrix of densely packed : Matrix of densely packed collagen fibers. Strong and nonelastic. Found in:collagen fibers. Strong and nonelastic. Found in:

• Tendons:Tendons: Attach muscles to bones. Attach muscles to bones.

• Ligaments:Ligaments: Attach bone to bone. Attach bone to bone.

E. E. CartilageCartilage: Rubbery matrix with collagen fibers. Found : Rubbery matrix with collagen fibers. Found on end of bones, nose, ears, and between vertebra.on end of bones, nose, ears, and between vertebra.

F. F. Bone:Bone: Supports the body of most vertebrates. Solid Supports the body of most vertebrates. Solid matrix of collagen fibers and calcium, phosphate, and matrix of collagen fibers and calcium, phosphate, and magnesium salts. Bone is harder than cartilage, but not magnesium salts. Bone is harder than cartilage, but not brittle because of collagen.brittle because of collagen.

Connective Tissue Binds and Provides Support

A. Loose Connective Tissue

B. Adipose Tissue

C. Blood

D. Fibrous Connective Tissue

E. Cartilage

F. Bone

3. Muscle Tissue3. Muscle Tissue Most abundant type of tissue in most animals. Most abundant type of tissue in most animals.

Accounts for two-thirds (2/3) of human weight.Accounts for two-thirds (2/3) of human weight. Specialized for Specialized for contractioncontraction. Made up of long cells . Made up of long cells

that contract when stimulated by that contract when stimulated by nerve impulsesnerve impulses.. Muscle cells have many Muscle cells have many microfilamentsmicrofilaments made up made up

of of actinactin and and myosinmyosin.. Muscle contraction accounts for much of energy Muscle contraction accounts for much of energy

consuming work in animals.consuming work in animals. Adults have a Adults have a fixed number of muscle cellsfixed number of muscle cells. .

Weight lifting doesn’t increase number of muscle Weight lifting doesn’t increase number of muscle cells, only their size.cells, only their size.

3. Muscle Tissue3. Muscle TissueThere are three types of muscle tissue:There are three types of muscle tissue:

A. A. Skeletal (striated) muscle Skeletal (striated) muscle : Attached to bones by : Attached to bones by

tendons. tendons.

Responsible for Responsible for voluntaryvoluntary movements. movements.

B. B. Cardiac muscleCardiac muscle: Forms contractile tissue of heart. : Forms contractile tissue of heart.

Not under voluntary controlNot under voluntary control..

C. C. Smooth muscle:Smooth muscle: Found in walls of digestive tract, Found in walls of digestive tract,

bladder, arteries, uterus, and many internal organs. bladder, arteries, uterus, and many internal organs.

Responsible for peristalsis and labor contractions. Responsible for peristalsis and labor contractions.

Contract more slowly than skeletal muscle, but can Contract more slowly than skeletal muscle, but can

remain contracted longer. remain contracted longer.

Not under voluntary controlNot under voluntary control..

4. Nervous Tissue4. Nervous Tissue Senses stimuli and transmits signals from one Senses stimuli and transmits signals from one

part of the animal to another.part of the animal to another. Controls the activity of muscles and glands, and Controls the activity of muscles and glands, and

allows the animal to allows the animal to respondrespond to its to its environmentenvironment.. NeuronNeuron: Nerve cell. Structural and functional : Nerve cell. Structural and functional

unit of nervous tissue. Consists of:unit of nervous tissue. Consists of:Cell body Cell body : Contains cell’s nucleus.: Contains cell’s nucleus.DendriteDendrite: Extension that conveys signals : Extension that conveys signals

towards the cell body. towards the cell body. Axon:Axon: Extension that transmits signals away Extension that transmits signals away

from the cell body. from the cell body. Supporting cellsSupporting cells: : Nourish, protect, and insulate Nourish, protect, and insulate

neurons.neurons.

ontractions.ontractions.Organs are made up of different tissuesOrgans are made up of different tissues Organ: Organ: Several tissues that act as a unit Several tissues that act as a unit

and together perform one or more and together perform one or more biological functions.biological functions.Perform functions that component tissues can’t Perform functions that component tissues can’t

carry out alone.carry out alone.

Example: The heart is an organ made up of:Example: The heart is an organ made up of:•• Muscle TissueMuscle Tissue: Contraction: Contraction

•• Epithelial TissueEpithelial Tissue: Lines heart chambers to prevent : Lines heart chambers to prevent leakage and provide a smooth surface.leakage and provide a smooth surface.

•• Connective TissueConnective Tissue: Makes heart elastic and : Makes heart elastic and strengthens its walls and valves.strengthens its walls and valves.

•• Nervous TissueNervous Tissue: Direct heart contractions.: Direct heart contractions.

Organs are Made of Several Different Tissues

Major Organ Systems in MammalsMajor Organ Systems in Mammals Digestive systemDigestive system Respiratory systemRespiratory system Circulatory systemCirculatory system

CardiovascularCardiovascularLymphatic and Immune systemLymphatic and Immune system

Excretory systemExcretory system Endocrine systemEndocrine system Reproductive systemReproductive system Nervous systemNervous system Muscular systemMuscular system Skeletal systemSkeletal system IntegumentaryIntegumentary

OOrgan systems must be coordinated for rgan systems must be coordinated for animal to surviveanimal to surviveOrgan systems interact with one another in Organ systems interact with one another in

order to maintain fairly stable conditions order to maintain fairly stable conditions (homeostasis) that are required for life.(homeostasis) that are required for life.

Example: Interactions between:Example: Interactions between:•• RespiratoryRespiratory

•• CirculatoryCirculatory

•• DigestiveDigestive

Animals Regulate their Internal Animals Regulate their Internal EnvironmentEnvironment

Homeostasis: Homeostasis: “Steady state”.“Steady state”. Internal environment of animal remains fairly Internal environment of animal remains fairly

constant despite changes in the external constant despite changes in the external environment.environment.

Control systems maintain internal conditions Control systems maintain internal conditions within a range in which life’s metabolic within a range in which life’s metabolic activities can occur.activities can occur.

Homeostasis is a Homeostasis is a dynamic statedynamic state resulting from resulting from changes in the outside environment and changes in the outside environment and internal control mechanisms that oppose such internal control mechanisms that oppose such changes.changes.

Animals Regulate their Internal Animals Regulate their Internal EnvironmentEnvironment

Homeostasis: Homeostasis: Maintained by Maintained by negative feedback mechanismsnegative feedback mechanisms..

A change in one condition (e.g.: low body A change in one condition (e.g.: low body temperature), results is a response that temperature), results is a response that counteractscounteracts that change (e.g.: shivering, etc.).that change (e.g.: shivering, etc.).

Internal conditions regulated by negative Internal conditions regulated by negative feedback:feedback:

•• Body temperature (Normal range: 97 Body temperature (Normal range: 97 -- 100100ooF)F)

•• Salt concentrationSalt concentration

•• pHpH

•• Blood levels of sugar, calcium, oxygen, etc.Blood levels of sugar, calcium, oxygen, etc.

Major Organ Systems in MammalsMajor Organ Systems in Mammals Digestive systemDigestive system Respiratory systemRespiratory system Circulatory systemCirculatory system

CardiovascularCardiovascularLymphatic and Immune systemLymphatic and Immune system

Excretory systemExcretory system Endocrine systemEndocrine system Reproductive systemReproductive system Nervous systemNervous system Muscular systemMuscular system Skeletal systemSkeletal system IntegumentaryIntegumentary

OOrgan systems must be coordinated for rgan systems must be coordinated for animal to surviveanimal to surviveOrgan systems interact with one another in Organ systems interact with one another in

order to maintain fairly stable conditions order to maintain fairly stable conditions (homeostasis) that are required for life.(homeostasis) that are required for life.

Example: Interactions between:Example: Interactions between:•• RespiratoryRespiratory

•• CirculatoryCirculatory

•• DigestiveDigestive