THE ANIMAL BODY AND
HOW IT MOVES
CHAPTER 22
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
Stratifie depithelium
in epidermis
Columnar epithelium
lining stomach
Bone
Cuboidal epithelium
in kidney tubules
Blood
Muscle tissues
Loose connective
tissue
Smooth muscle in
intestinal wall
Skeletal muscle in
voluntary muscles
Cardiac muscle in
heart
ORGANIZATION OF THE
VERTEBRATE BODY
• 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:
Cardiac
muscle
Organ system:
Circulatory system
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 has a secretory function and
often forms glands.
TABLE 22.2
EPITHELIAL TISSUE
Tissue
Typical Location
Tissue Function
Lining of lungs,
capillary walls,
and blood vessels
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
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
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
Pseudostratified Epithelium
5
Columnar
Cilia
Pseudo–
stratified
columnar
cell
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.
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 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.
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 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.
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
• New bone is formed in
two stages:
• First, osteoblasts lay
down collagen fibers
along lines of stress.
• Then calcium minerals
impregnate the fibers.
Haversian
system
Red marrow
in spongy bone
Capillary in
central canal
Lacunae
containing
osteocytes
Compact
bone
Lamellae
• 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).
Spongy
bone
Compact
bone
CONNECTIVE TISSUE SUPPORTS THE
BODY
• There is dynamic bone “remodeling” going
on all the time.
• Osteoblasts deposit bone, while osteoclasts break
down bone and release calcium.
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 and myosin make up the
myofilaments.
• There are three different kinds of muscle in
vertebrates:
• Smooth muscle
• Skeletal muscle
• Cardiac muscle
MUSCLE TISSUE LETS THE BODY
MOVE
• Smooth muscle cells are long and spindleshaped.
• 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,
and each myofibril contains
many myofilaments (the
proteins actin and myosin).
A SKELETAL MUSCLE FIBER, OR MUSCLE
CELL
Sarcoplasmic reticulum
Striations
Myofibrils
Nucleus
Myofilaments of
actin and myosin
Mitochondria
MUSCLE TISSUE LETS THE
BODY MOVE
• 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.
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 axon that is a single, long extension which carries
nerve impulses away from the body.
• Some axons can be quite long.
Cell body
Dendrites
Axon
Direction of
nerve impulse
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 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 22.10 Snakes have an
endoskeleton
Figure 22.9 Crustaceans
have an exoskeleton
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 forms the
shoulder joint.
• Pelvic girdle forms the hip
joint.
Skull
Scapula
(shoulder blade)
Sternum
Ribs
Humerus
Vertebral
column
Radius
Pelvis
Ulna
Carpals
(wrist)
Metacarpals
(hand)
Femur
Phalanges
(fingers)
Patella
Tibia
Fibula
Tarsals
(ankle)
Metatarsals
(foot)
Phalanges
(toes)
MUSCLES AND HOW THEY
WORK
• Skeletal muscles move
the bones of the
skeleton.
Pectoralis
major
Biceps
Origin of muscle
• Tendons are straps of
dense connective tissue
that attach muscles to
bone.
• Bones pivot about flexibleInsertion of muscle
connections called joints.
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 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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
2
Myosin head
Actin
Myosin
filament
The myosin head is attached to actin.
The myosin head flexes, advancing the actin filament.
3
4
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.
35
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1
Sarcomere
Z line
Actin
Myosin
Myosin
head
Z line
The heads on the two ends of the myosin filament are oriented in opposite directions.
KEY
BIOLOGICAL
PROCESS:
THE SLIDING
FILAMENT
MODEL
2
Z line
Z line
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.
3
Z line
Z line
The result is that both Z lines move toward the center—and contraction occurs.
36
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++, 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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