CHAPTER 22 THE ANIMAL BODY AND HOW IT MOVES. INNOVATIONS IN BODY DESIGN Several evolutionary...

CHAPTER 22

THE ANIMAL BODY AND HOW IT MOVES

INNOVATIONS IN BODY DESIGN

• Several evolutionary innovations in the design of animal bodies have led to the diversity seen in the kingdom Animalia.• Radial versus bilateral symmetry.• No body cavity versus body cavity.• Nonsegmented versus segmented bodies.• Incremental growth versus molting.• Protostomes versus deuterostomes.

ORGANIZATION OF THE VERTEBRATE BODY

• All vertebrates have the same general architecture: a long internal tube that extends from mouth to anus, which is suspended within an internal body cavity called the coelom.• The coelom of many terrestrial vertebrates is

divided into two parts.• Thoracic cavity contains the heart and lungs.• Abdominal cavity contains the stomach,

intestines, and liver.


• A tissue is a group of cells of the same type that performs a particular function.

• There are four general classes of tissues:• epithelial• connective• muscle• nerve

VERTEBRATE TISSUE TYPESEpithelialtissues

Nerve tissue Connectivetissues

Columnar epitheliumlining stomach

Stratifie depitheliumin epidermis

Bone

Blood

Loose connectivetissue

Cuboidal epitheliumin kidney tubules

Muscle tissues

Smooth muscle inintestinal wall

Skeletal muscle involuntary muscles

Cardiac muscle inheart


• Organs are body structures comprised of several different tissues grouped together into a larger structural and functional unit.

• An organ system is a group of organs that work together to carry out an important function.

Organ:Heart

Tissue:Cardiacmuscle

Organ system:Circulatory system

Cell:Cardiac muscle cell


• There are 11 principal organ systems in the vertebrate body:

• skeletal• circulatory• endocrine• nervous• respiratory• immune and

lymphatic

• digestive• urinary• muscular• reproductive • integumentary

EPITHELIUM IS PROTECTIVE TISSUE

• The epithelium functions in three ways:• 1) To protect the tissues

beneath them from dehydration.

• 2) To provide sensory surfaces.• Many of a vertebrate’s

sense organs are modified epithelial cells.

• 3) To secrete materials.• Most secretory glands

are derived from pockets of epithelial cells.


• Epithelial cells are classified into three types according to their shapes: squamous, cuboidal, or columnar.

• Layers of epithelial tissue are usually one or two cells thick but the sheets of cells are tightly bound together.

• Epithelium possesses remarkable regenerative abilities.


• There are two general kinds of epithelial tissue:• Simple epithelium is only one cell layer thick

and is important for exchanging materials across it.

• Stratified epithelium is multiple cell layers in thickness and provides cushioning and protection• Found in the skin, it is continuously replaced.

• Cuboidal epithelium has a secretory function and often forms glands.

1 Lining of lungs,capillary walls,and blood vessels

Flat and thin cells; providesa thin layer across whichdiffusion can readily occur;the cells when viewed fromthe surface look like tiles ona floor

2 Lining of someglands and kidneytubules; coveringof ovaries

Cells rich in specific transportchannels; functions insecretion and specificabsorption

3 Surface lining ofstomach, intestines,and parts of respiratorytract

Thicker cell layer; providesprotection and functions insecretion and absorption

Stratified Epithelium

4 Outer layer of skin;lining of mouth

Tough layer of cells; providesprotection

Pseudostratified Epithelium

5 Lining of parts ofrespiratory tract

Functions in secretionof mucus; dense with cilia(small, hairlike projections)that aid in movement ofmucus; provides protection

Tissue

TABLE 22.2 EPITHELIAL TISSUETypical Location Tissue Function

Simple Epithelium

Simplesquamousepithelialcell

Nucleus

Squamous

Cuboidal

Columnar

Cuboidalepithelialcells

Nucleus

Cytoplasm

Columnarepithelialcells

Nucleus

Goblet cell

Squamous

Stratifiedsquamouscells

Nuclei

ColumnarCilia

Pseudo–stratifiedcolumnarcell

Goblet cell

(1, 4): © The McGraw-Hill Companies, Inc./Al Telser, photographer; (2, 3, 5): © Ed Reschke

CONNECTIVE TISSUE SUPPORTS THE BODY

• Connective tissue cells fall into three functional categories:• Defense (cells of the immune system).• Support (cells of the skeletal system).• Storage and distribution (blood and fat

cells).

• All connective tissues share a common structural feature.• Have abundant extracellular material, called

the matrix, between widely spaced cells.


• Immune cells roam the body within the bloodstream and hunt invading microorganisms and cancer cells.• There are two kinds of immune cells:

• Macrophages that engulf and digest invaders.

• Lymphocytes that attack virus-infected cells or make antibodies.

• These cells are collectively known as “white blood cells”.


• Three kinds of connective tissue are the principal components of the skeletal system.• Fibrous connective tissue is made up by

cells called fibroblasts that secrete structurally strong proteins in the spaces between the cells.

• Collagen protein is an example.• Cartilage is firm but flexible due to its

configuration of collagen.• Bone is stronger than cartilage because the

collagen is coated with calcium phosphate salt, making the tissue rigid.


• Some connective tissue cells are specialized to accumulate and transport particular molecules.• Adipose tissue is made up of fat-accumulating

cells that contain vacuoles for storing fat.• Erythrocytes are red blood cells that transport

O2 and CO2 in blood.

• In addition, the red blood cells move in the plasma, which is a solvent for many substances.


• The vertebrate endoskeleton is strong because of the structural nature of bone.

• Bone is a dynamic tissue that is constantly being reconstructed.• The outer layer of bone is very dense and

compact and called compact bone.• The interior of bone has a more open lattice

structure and is called spongy bone.• Red blood cells form in the marrow of spongy

bone.


• New bone is formed in two stages:• First, osteoblasts lay

down collagen fibers along lines of stress.

• Then calcium minerals impregnate the fibers.

• Bone is laid down in thin, concentric layers.• The layers form as a

series of tubes around a narrow central channel called a central canal (Haversian canal).

Red marrowin spongy bone

Capillary incentral canal

Haversiansystem

Lacunaecontainingosteocytes

Lamellae

Compactbone

Compactbone

Spongybone


• There is dynamic bone “remodeling” going on all the time.• Osteoblasts deposit bone, while osteoclasts

break down bone and release calcium.


• As a person ages, the backbone and other bones tend to decline in mass.• Excessive bone

loss is a condition called osteoporosis.

MUSCLE TISSUE LETS THE BODY MOVE

• Muscle cells are the motors of the vertebrate body.• They have many contractible protein fibers,

called myofilaments, inside of them.• The proteins actin and myosin make up the

myofilaments.• There are three different kinds of muscle in

vertebrates:• Smooth muscle• Skeletal muscle• Cardiac muscle


• Smooth muscle cells are long and spindle-shaped.• Each cell contains a single nucleus.• Smooth muscle is the least organized of the

types of muscle tissue.• It is found in areas such as the walls of blood

vessels and the gut.


• Skeletal muscle moves the bones of the skeleton.• Skeletal muscles fuse to form

one very long fiber with the nuclei pushed out to the periphery of the cytoplasm.

• Each muscle fiber consists of many elongated myofibrils, and each myofibril contains many myofilaments (the proteins actin and myosin).

A SKELETAL MUSCLE FIBER, OR MUSCLE CELL

Striations

Nucleus

Mitochondria

Myofilaments ofactin and myosin

Sarcoplasmic reticulum

Myofibrils


• Cardiac muscle is comprised of chains of single cells, each with its own nucleus.• These chains are organized into

fibers that branch and interconnect to form a network.

• Each muscle cell is coupled to its neighbors electrically by gap junctions.• An electrical impulse passes

from cell to cell across the gap junctions, causing the heart to contract in an orderly fashion.

NERVE TISSUE CONDUCTS SIGNALS RAPIDLY

• Nerve cells carry information rapidly from one vertebrate organ to another.

• Nerve tissue is comprised of two types of cells:• Neurons are specialized for transmitting nerve

impulses.• Glial cells are supporting cells that supply

neurons with nutrition, support, and insulation.


• Each neuron is comprised of three parts:• A cell body that contains the nucleus.• Dendrites that extend from the cell body and act

as antennae to receive nerve impulses.• An axon that is a single, long extension which

carries nerve impulses away from the body.• Some axons can be quite long.

Dendrites Cell body

Axon

Direction ofnerve impulse

Nucleus


• Neurons have three general categories:• Sensory neurons

• Carry electrical impulses from the body to the central nervous system.

• Motor neurons• Carry electrical impulses from the central nervous

system to the muscles.• Association neurons

• Occur within the central nervous system and act as connectors between the sensory and motor neurons.

• Neurons are connected by a tiny gap called a synapse.• Communication is via neurotransmitters

TYPES OF SKELETONS

• Animals are able to move because the opposite ends of their muscles are attached to a rigid scaffold, or skeleton.• There are three types of skeletons in the animal

kingdom:• Hydraulic skeletons are fluid-filled cavities

encircled by muscles that raise the pressure of the fluid when they constrict.

• Exoskeletons surround the body as a rigid, hard case to which muscles attach internally.

• Endoskeletons are rigid internal skeletons to which muscles are attached.

Figure 22.8 Earthworms have a hydraulic skeleton

Figure 22.9 Crustaceans have an exoskeleton

Figure 22.10 Snakes have an endoskeleton

TYPES OF SKELETONS

• The human skeleton is made up of 206 bones.• Axial skeleton is up of the

skull, backbone, and rib cage.• Appendicular skeleton is

made up of the bones of the arms and legs and the girdles where they attach to the axial skeleton.

• Pectoral girdle forms the shoulder joint.

• Pelvic girdle forms the hip joint.

Skull

Clavicle Scapula(shoulder blade)

RibsSternum

Humerus

Vertebralcolumn

Radius

Ulna

Femur

Patella

Tarsals(ankle)

Metatarsals(foot)

Phalanges(toes)

Fibula

Tibia

Phalanges(fingers)

Metacarpals(hand)

Carpals(wrist)

Pelvis

MUSCLES AND HOW THEY WORK

• Skeletal muscles move the bones of the skeleton.• Tendons are straps of

dense connective tissue that attach muscles to bone.

• Bones pivot about flexible connections called joints.

Origin of muscle

Pectoralismajor

Biceps

Rectusabdominis

Sartorius

Quadriceps

Gastrocnemius

Insertion of muscle


• Muscles can only pull because myofibrils contract rather than expand.• The muscles in the movable joints of

vertebrates are attached in opposing pairs called flexors and extensors.• When contracted they move the bones in

different directions.Extensors(quadriceps)

Flexor(hamstring)


• The sliding filament model of muscular contraction describes how actin and myosin cause muscles to contract.• The head of a myosin filament binds to an actin

filament.• When the muscle contracts, the myosin head

flexes and pulls the actin it is attached to along with it .

• ATP is used to release and unflex the myosin head.

KEY BIOLOGICAL PROCESS: MYOFILAMENT CONTRACTION

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1 2

43

Myosin headActin

Myosinfilament

ATP

The myosin head is attached to actin. The myosin head flexes, advancing the actin filament.

The myosin head releases and unflexes, powered by ATP. The myosin head reattaches to actin, farther along the fiber.


• As one myosin head after another flexes, the myosin in effect “walks” step by step along the actin.

• The contractile unit of muscle is called a sarcomere.• The actin filaments are anchored to one end of the

sarcomere called the Z line.• Myosin is interspersed between a pair of actin

filaments connected to either end of the sarcomere.• As the actin filaments are pulled by myosin, so are

the Z lines; the sarcomere shortens, and the cell contracts.

35

36

KEY BIOLOGICAL PROCESS:

THE SLIDING

FILAMENT MODEL

1

2

3

The heads on the two ends of the myosin filament are oriented in opposite directions.

Thus, as the right-hand end of the myosin filament “walks” along the actin filaments, pulling them and their attached Z line leftwardtoward the center, the left-hand end of the same myosin filament “walks” along the actin filaments, pulling them and theirattached Z line rightward toward the center.

The result is that both Z lines move toward the center—and contraction occurs.

Sarcomere

Z line Actin Myosin Z lineMyosinhead

Z line Z line

Z lineZ line

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


• In a relaxed muscle, access to actin by myosin is normally blocked by a regulatory protein called tropomyosin.

• In the presence of Ca++, the tropomyosin shifts away to expose binding sites on the actin for myosin.• Muscle fibers store Ca++ in a modified

endoplasmic reticulum called the sarcoplasmic reticulum.

• When nerves stimulate muscles to contract, Ca+

+ is released from the sarcoplasmic reticulum.

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