GEORGE B. JOHNSON Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction...

GEORGE B. JOHNSON

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display

PowerPoint® Lectures prepared by Johnny El-Rady

19 The Animal Body And How It Moves

Essentials ofThe Living

WorldFirst Edition


19.1 Innovations in Body Design

Four key innovations have led to the diversity seen in the phylum Animalia


In radial symmetry, the parts of the body are arranged around a central axis

In bilateral symmetry, the body has a right and left half that are mirror images of each other

Allows different organs to be located in different parts of the body

Ultimately led to cephalizationEvolution of a definite head and brain area

Radial Versus Bilateral Symmetry


The body cavity supports organs, distributes materials and fosters complex developmentThree body arrangements

Acoelomates: No body cavityExample: Sponges and flatworms

Pseudocoelomates: Body cavity (pseudocoel) forms between the endoderm and mesoderm

Example: Nematodes

Coelomates: Body cavity (coelom) forms entirely within the mesoderm

Example: Mollusks, arthropods and vertebrates

No Body Cavity Versus Body Cavity


Segmentation is the subdivision of the body into segments

Two advantages result from embryonic segmentation1. Each segment may develop a more or less complete set of adult organ systems

2. Locomotion is far more effective because of increased flexibility of movement

Nonsegmented Versus Segmented Bodies


Deuterostomes evolved from protostomes > 630 myaWhile both are coelomates, they differ in three aspects of embryonic growth

Protostomes Versus Deuterostomes

Protostomes Deuterostomes

How cleavage forms a hollow ball of cells

Spiral cleavage Radial cleavage

How the blastopore determines body axis

Blastopore forms the mouth

Blastopore forms the anus

How developmental fate of embryo is fixed

Determinate cleavage

Indeterminate cleavage


TABLE 19.1


19.2 Organization of theVertebrate Body

All vertebrates have the same general architecture:

Food flows through a long tube from mouth to anus Tube is suspended in coelom, which is divided into

Thoracic cavity – Heart and lungsAbdominal cavity – Stomach and intestines

Body is supported by a skeleton made up of jointed bones

The skull protects the brainThe vertebral column protects the spinal cord


TissuesCells of the same type are organized into tissuesTissues form as the vertebrate body developsThree fundamental layers of cells

Endoderm ; Mesoderm ; EctodermThey differentiate into > 100 different cell types

Adult tissues are grouped into 4 general classesEpithelialConnective MuscleNerve


Fig. 19.1 Vertebrate tissue types


OrgansStructures composed of several different tissues grouped into large structural and functional units

Organ systemsGroups of organs that work together to carry out an important function

Fig. 19.2 Levels of organization within the vertebrate body


Vertebrates contain 11 principal organs systemsSkeletal system

Bones, skull, cartilage, ligaments

Circulatory systemHeart, blood vessels, blood

Fig. 19.3


Vertebrates contain 11 principal organs systemsEndocrine system

Pituitary, adrenal, ductless glands

Nervous systemNerve, sense organs, brain, spinal cord

Fig. 19.3


Vertebrates contain 11 principal organs systemsRespiratory system

Lungs, trachea, other air passages

Immune systemLymphocytes, macrophages, thymus, lymph nodes

Fig. 19.3


Vertebrates contain 11 principal organs systemsDigestive system

Mouth, esophagus, stomach, intestines

Urinary systemKidneys, bladder, associated ducts

Fig. 19.3


Vertebrates contain 11 principal organs systemsMuscular system

Skeletal, cardiac and smooth muscles

Integumentary systemSkin, hair, nails and sweat glands

Fig. 19.3


Vertebrates contain 11 principal organs systemsReproductive system

Testes or ovariesAssociated structures

Fig. 19.3


19.3 Epithelium is Protective TissueThe vertebrate body consists of one tube (digestive tract) suspended into another (body cavity: coelom)

The outside of the body is covered with cells (skin) derived from embryonic ectoderm tissue

The body cavity is lined with cells derived from embryonic mesoderm tissue

The hollow inner core of the digestive tract is lined with cells derived from embryonic endoderm tissue


Epithelial cells are produced from all 3 germ layersCollectively called the epitheliumThree important functions

1. Protect tissues from dehydration and mechanical damage

2. Provide sensory surfaces

3. Secrete materials Fig. 19.4

Gila monster

Tough, scaly skin

Epithelium possesses amazing regenerative abilities


Epithelial cells are classified into three types according to their shape

Squamous

Cuboidal

Columnar

Table 19.2


There are three general kinds of epithelial tissueSimple epithelium

Only a single layer thickFound in the lining of the lungs and major body cavities

Stratified epitheliumSeveral layers thickFound in the skin

GlandsInvolved in secretionEndocrine glands secretes hormones into the bloodExocrine glands use ducts to secrete sweat, milk, saliva and digestive enzymes out of the body


19.4 Connective TissueSupports the Body

Connective tissue is derived from the mesodermThree functional categories

1. Immune systemBody defense

2. Skeletal systemBody support

3. Blood and fat cellsStorage and distribution of substances


Two principal immune cells are

Immune Connective Tissue

2. LymphocytesMake antibodies

OrAttack virus-infected or cancerous cells

1. MacrophagesEngulf and digest invading microbes

Table 19.3


1. FibroblastsThe most common kindSecrete structurally strong proteins such as collagen into spaces between cells

Skeletal Connective Tissue

2. Cartilage Collagen matrix forms in long parallel arrays along lines of mechanical stressFound in joint surfaces

3. BoneCollagen fibers are coated with calcium phosphate

Table 19.3


Includes

Storage and Transport Connective Tissue

Erythrocytes (RBC)Transport O2 and CO2 in the blood

Adipose tissueAccumulates fat

The fluid portion of blood is called plasma

Table 19.3

Contains nutrients, wastes and antibodies


Bone is a dynamic tissue that is constantly being reconstructed

Outer layer is very dense and compactCalled compact bone

Interior is a more open lattice structure Called spongy bone

A Closer Look at Bone


New bone is formed in two stages1. A matrix of collagen fibrils is secreted by cells called osteoblasts2. The fibrils are impregnated by crystals of a calcium phosphate mineral called hydroxyapatite

Bone is laid down in thin layers around a narrow central channel

This central canal (or Haversian canal) runs parallel to the length of the bone

A Closer Look at Bone


Fig. 19.5 The structure of bone


Two cell types are responsible for bone “remodeling” during growthOsteoblasts

Deposit boneOsteoclasts

Secrete enzymes that digest the bone matrix

OsteoporosisExcessive bone lossUsually associated with aging Fig. 19.6

Equal osteoblast and osteoclast

activities

Excess osteoclast activity


19.5 Muscle TissueLets the Body Move

The distinguishing characteristic of muscle cells is the abundance of contractible protein fibers

These microfilaments (myofilaments) are made up of actin and myosin

Muscle contraction occurs when actin and myosin slide past each other

The vertebrate body possesses three different kinds of muscle cells

Smooth Skeletal Cardiac


Cells are long and spindle-shapedEach contains a single nucleus

Cellular microfilaments are loosely organized

Smooth Muscle

Power rhythmic involuntary contractions

Table 19.4

Sheets of cells

Found in the walls of blood vessels, stomach and intestines


Produced by fusion of several cells at their endsThis creates a very long muscle fiber that contains all the original nuclei

Skeletal Muscle

Microfilaments are bunched together into myofibrils

Found in voluntary muscles

Power voluntary contractions

Table 19.4

Striated


Fig. 19.7 A muscle fiber, or muscle cell

Modified ER


Composed of chains of single cells, each with its own nucleus

Chains are interconnected, forming a latticework

Cardiac Muscle

Each heart cell is coupled to its neighbors by gap junctions

Table 19.4Allow electrical signals between cells

Cause orderly pulsation of heart

Striated


19.6 Nerve TissueConducts Signals Rapidly

Nerve tissue is composed of two kinds of cells

1. Neurons Specialized for the transmission of nerve impulses

2. Glial cellsSupport neurons with nutrients, support and insulation


19.6 Nerve TissueConducts Signals Rapidly

Neuron plasma membranes are rich in ion-selective channels

These maintain a voltage difference between the cell’s interior and exterior

Depolarization is the temporary loss of this voltage difference

It results in a wave of electrical activity, or nerve impulse


Each neuron consists of three parts

1. Cell body – Contains the nucleus2. Dendrites – Bring nerve impulses to the cell3. Axon – Carry nerve impulses away from the cell

Fig. 19.8


Neurons are separated by tiny gaps termed synapses

Neurons communicate by passing neurotransmitters across these synapses

Note: A nerve is made up of the axons of many neurons


TABLE 19.5


19.7 Types of SkeletonsThere are three types of skeletons in animals

1. Hydraulic skeletonFluid-filled cavity encircled by muscle fibers

Found in soft-bodied invertebrates like jellyfish

Fig. 19.9


2. ExoskeletonRigid hard case surrounding the bodyFound in arthropods

3. EndoskeletonRigid internal skeleton to which muscles attachFound in vertebrates and echinoderms

Fig. 19.10

Rock crab

Exoskeleton made up of

chitin

Fig. 19.11

Endoskeleton made up of

bone


Made up of 206 individual bones

Axial skeletonSupports the main body axisSkull, backbone (spine) and rib cage80 bones in all

Appendicular skeletonSupports the arm and legsPectoral and pelvic girdles126 bones in all

The Human Skeleton


Fig. 19.12 Axial and appendicular skeletons


19.8 Muscles and How They Work

The major human muscles include the following

Fig. 19.13


19.8 Muscles and How They Work

Skeletal muscles are attached to bones by straps of connective tissue called tendons

Bones pivot about flexible joints pulled back and forth by attached muscles

The origin of the muscle is the end attached by a tendon to a stationary bone

The insertion is the end attached to a bone that moves during muscle contraction


Muscles in movable joints are attached in opposing pairs

Flexors retract limbsExtensors extend limbs

Fig. 19.14


Limb movement is always the result of muscle contraction

Never muscle extension

There are two types of muscle contraction

IsotonicMuscle shortens, thus moving the bones

IsometricMuscle does not shorten, but it exerts a force


Myofilaments are made up of actin and myosinActin filaments consist of two chains of actin molecules wrapped around one anotherMysosin filaments also consist of two chains wound around each other

One end consists of a very long rodThe other consists of a double-headed globular region or “head”

Muscle Contraction

Fig. 19.15


An ATP-powered myosin head-flex mechanism allows the actin filament to slide past myosin

This causes myofilament contraction


Fig. 19.16 How actin and myosin filaments interact


In vertebrate skeletal muscle, contraction is initiated by a nerve impulse

Nerve fibers are embedded in the surface of the muscle fiber forming a neuromuscular junction

When a signal reaches the end of a neuronThe neuron releases acetylcholine into the gap between neuron and muscle

This causes depolarization of the muscle cell


When a muscle is relaxed, attachment sites for myosin heads are blocked by tropomyosin

Role of Calcium Ions in Contraction

For the muscle to contract, tropomyosin must be moved by another protein called troponin

The troponin-tropomyosin complex is regulated by calcium ion concentrations in the muscle cell


Absence of Ca++ Muscle is relaxed

Muscle contracts

Fig. 19.17 How calcium controls muscle contraction

Presence of Ca++


Muscle fibers store Ca++ in the sarcoplasmic reticulum

Role of Calcium Ions in Contraction

Nerve activity causes the release of Ca++ and ultimately muscle contraction

Fig. 19.18

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