Chapter 22

Transcript Chapter 22

THE ANIMAL BODY AND HOW IT MOVES

C H A P T E R 2 2

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.

ORGANIZATION OF THE VERTEBRATE BODY

• • 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 TYPES

Nerve tissue Epithelial tissues Connective tissues Columnar epithelium lining stomach Stratifie depithelium in epidermis Bone Cuboidal epithelium in kidney tubules Muscle tissues Blood Smooth muscle in intestinal wall Skeletal muscle in voluntary muscles Cardiac muscle in heart Loose connective tissue

ORGANIZATION OF THE VERTEBRATE BODY

• •

Organs

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

organ system

work together to carry out an is a group of organs that important function.

Organ: Heart Organ system: Circulatory system Tissue: Cardiac muscle Cell: Cardiac muscle cell

ORGANIZATION OF THE VERTEBRATE BODY

• 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.

EPITHELIUM IS PROTECTIVE TISSUE

• • • 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.

EPITHELIUM IS PROTECTIVE TISSUE

• 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

often forms glands.

has a secretory function and

TABLE 22.2 EPITHELIAL TISSUE Tissue Simple Epithelium 1 Squamous Simple squamous epithelialcell Nucleus 2 Cuboidal Cuboidal epithelial cells Nucleus Cytoplasm 3 Columnar Columnar epithelial cells Nucleus Goblet cell Stratified Epithelium 4 Squamous Stratified squamous cells Nuclei Typical Location Lining of lungs, capillary walls, and blood vessels Tissue Function Flat and thin cells; provides a thin layer across which diffusion can readily occur; the cells when viewed from the surface look like tiles on a floor Lining of some glands and kidney tubules; covering of ovaries Cells rich in specific transport channels; functions in secretion and specific absorption Surface lining of stomach, intestines, and parts of respiratory tract Thicker cell layer; provides protection and functions in secretion and absorption Outer layer of skin; lining of mouth Tough layer of cells; provides protection Pseudostratified Epithelium 5 Columnar Cilia Pseudo – stratified columnar cell Goblet cell Lining of parts of respiratory tract Functions in secretion of mucus; dense with cilia (small, hairlike projections) that aid in movement of mucus; provides protection

(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 Support

(cells of the immune system).

(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.

CONNECTIVE TISSUE SUPPORTS THE BODY

• 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”.

CONNECTIVE TISSUE SUPPORTS THE BODY

• Three kinds of connective tissue are the principal components of the skeletal system.

•

Fibrous connective tissue

is made up by cells • • called proteins in the spaces between the cells.

•

fibroblasts Collagen

that secrete structurally strong 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.

CONNECTIVE TISSUE SUPPORTS THE BODY

• 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

and CO 2 are red blood cells that transport O 2 in blood.

• In addition, the red blood cells move in the

plasma

, which is a solvent for many substances.

CONNECTIVE TISSUE SUPPORTS THE BODY

• • 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.

• •

CONNECTIVE TISSUE SUPPORTS THE BODY

Haversian system

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 marrow in spongy bone Capillary in central canal Lacunae containing osteocytes Compact bone Lamellae Spongy bone Compact bone

CONNECTIVE TISSUE SUPPORTS THE BODY

• There is dynamic bone “remodeling” going on all the time.

•

Osteoblasts

deposit bone, while

osteoclasts

down bone and release calcium.

break

CONNECTIVE TISSUE SUPPORTS THE BODY

• 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

myofilaments.

and

myosin

make up the There are three different kinds of muscle in vertebrates: • • •

Smooth muscle Skeletal muscle Cardiac muscle

MUSCLE TISSUE LETS THE BODY MOVE

•

Smooth muscle

shaped.

• • • cells are long and spindle 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.

MUSCLE TISSUE LETS THE BODY MOVE

•

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

many myofilaments (the proteins actin and myosin).

and each myofibril contains

A SKELETAL MUSCLE FIBER, OR MUSCLE CELL

Sarcoplasmic reticulum Striations Nucleus Myofibrils Myofilaments of actin and myosin Mitochondria

MUSCLE TISSUE LETS THE BODY MOVE

•

Cardiac muscle

chains of single cells, each with its own nucleus.

is comprised of • • 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

impulses.

are specialized for transmitting nerve

Glial cells

are supporting cells that supply neurons with nutrition, support, and insulation.

NERVE TISSUE CONDUCTS SIGNALS RAPIDLY

• 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 nerve impulses away from the body.

•

axon

that is a single, long extension which carries Some axons can be quite long.

Dendrites Cell body Axon Direction of nerve impulse Nucleus

NERVE TISSUE CONDUCTS SIGNALS RAPIDLY

• • 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

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

are fluid-filled cavities encircled • •

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

Clavicle

• 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

shoulder joint.

forms the •

Pelvic girdle

forms the hip joint.

Ribs Pelvis Carpals (wrist) Metacarpals (hand) Phalanges (fingers) Tibia Fibula Skull Scapula (shoulder blade) Sternum Humerus Vertebral column Radius Ulna Femur Patella Tarsals (ankle) Metatarsals (foot) Phalanges (toes)

MUSCLES AND HOW THEY WORK

• Skeletal muscles move the bones of the skeleton.

• •

Origin of muscle Tendons

bone.

are straps of dense connective tissue that attach muscles to Bones pivot about flexible connections called

joints .

Insertion of muscle Pectoralis major Biceps Rectus abdominis Sartorius Quadriceps Gastrocnemius

MUSCLES AND HOW THEY WORK

• 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.

Flexor (hamstring) Extensors (quadriceps)

MUSCLES AND HOW THEY WORK

• The

sliding filament model

contraction describes how actin and myosin cause muscles to contract.

of muscular • • • 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.

1 Myosin filament

KEY BIOLOGICAL PROCESS: MYOFILAMENT CONTRACTION

2 Myosin head Actin 3 The myosin head is attached to actin.

4 The myosin head flexes, advancing the actin filament.

ATP The myosin head releases and unflexes, powered by ATP.

The myosin head reattaches to actin, farther along the fiber.

MUSCLES AND HOW THEY WORK

• • 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.

Sarcomere Z line Actin Myosin Myosin head Z line KEY BIOLOGICAL PROCESS: THE SLIDING FILAMENT MODEL 2 The heads on the two ends of the myosin filament are oriented in opposite directions.

Z line Z line 3 Thus, as the right hand end of the myosin filament “walks” along the actin filaments, pulling them and their attached Z line leftward toward the center, the left hand end of the same myosin filament “walks” along the actin filaments, pulling them and their attached Z line rightward toward the center.

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

Z line

MUSCLES AND HOW THEY WORK

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

tropomyosin .

In the presence of Ca actin for myosin.

++ , the tropomyosin shifts away to expose binding sites on the • • Muscle fibers store Ca endoplasmic reticulum called the sarcoplasmic reticulum.

++ in a modified When nerves stimulate muscles to contract, Ca ++ is released from the sarcoplasmic reticulum.

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