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Chapter 42
The Animal Body and
Principles of
Regulation
Organization of Vertebrate Body
• There are four levels of
organization
1. Cells
2. Tissues
3. Organs
4. Organ systems
• Bodies of vertebrates are
composed of different cell types
– Humans have 210
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Organization of Vertebrate Body
• Tissues
• Groups of cells that are similar in structure
and function
• 3 fundamental embryonic tissues are called
germ layers
• Endoderm, mesoderm, and ectoderm
• In adult vertebrates, there are four primary
tissues
• Epithelial, connective, muscle, and nerve
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Organization of Vertebrate Body
• Organs
– Combinations of different tissues that form a
structural and functional unit
• Organ systems
– Groups of organs that cooperate to perform
the major activities of the body
– Vertebrate body contains 11 principal organ
systems
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Organization of Vertebrate Body
• General body plan of all vertebrates is essentially a tube
within a tube
– Inner tube – digestive tract
– Outer tube – main vertebrate body
• Supported by a skeleton
– Outermost layer – skin and its accessories
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Organization of Vertebrate Body
• 2 main body cavities
– Dorsal body cavity
• Forms within skull and
vertebrae
– Ventral body cavity
• Bounded by the rib
cage and vertebral
column
• Divided by the
diaphragm into
• Thoracic cavity –
heart and lungs
• Abdominopelvic
cavity – most
organs
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Epithelial Tissue
• An epithelial membrane, or epithelium,
covers every surface of the vertebrate
body
• Can come from any of the 3 germ layers
• Some epithelia change into glands
• Cells of epithelia are tightly bound together
– Provide a protective barrier
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Epithelial Tissue
• Epithelia possess remarkable regenerative
powers replacing cells throughout life
• Epithelial tissues attach to underlying
connective tissues by a fibrous membrane
– Basal surface – secured side
– Apical surface – free side
– Inherent polarity important for their function
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Epithelial Tissue
• Two general classes
• Simple – one layer thick
• Stratified – several layers thick
• Each class subdivided into
• Squamous cells – flat
• Cuboidal cells – about as wide as tall
• Columnar cells – taller than they are wide
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Simple Epithelium
• Simple squamous epithelium
– Lines lungs and blood
capillaries
– Delicate nature permits
diffusion
• Simple cuboidal epithelium
– Lines kidney tubules and
several glands
• Simple columnar epithelium
– Lines airways of respiratory
tract and most of the
gastrointestinal tract
– Contains goblet cells –
secrete mucus
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•
•
Lines capillaries
Lines aveoli in lungs
•
This is a cross-section of a kidney
tubule
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• Cross-section of small
intestine
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Simple Epithelium
• Exocrine glands
• Connected to epithelium by a duct
• Sweat, sebaceous, and salivary glands
• Endocrine glands
• Ductless – lost duct during development
• Secretions (hormones) enter blood
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Stratified Epithelium
• 2 to several layers thick
• Named according to the features of their apical cell
layers
• Epidermis is a stratified squamous epithelium
– Terrestrial vertebrates have a keratinized
epithelium
• Contains water-resistant keratin
– Lips are covered with nonkeratinized, stratified squamous epithelium
15
Connective Tissues
• Derive from embryonic mesoderm
• All have abundant extracellular material
called the matrix
– Protein fibers plus ground substance
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• Divided into two major classes:
• Connective tissue proper
• Loose
• Fibroblasts, some immune cells (mast cells and
macrophages), adipose (fat)
• Supports organs
• Dense
• Stronger, more tightly packed collagen
• Tendons, sheath around muscles
• Special connective tissue
• Cartilage
• Bone
• blood
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Connective Tissue Proper
• Fibroblasts produce and secrete extracellular matrix
• Loose connective tissue
– Cells scattered within a matrix that contains a large amount of
ground substance
– Strengthened by protein fibers
• Collagen – supports tissue
• Elastin – makes tissue elastic
• Reticulin – helps support the network of collagen
18
Connective Tissue Proper
• Adipose cells (fat cells) also occur in loose
connective tissue
– Develop in large groups in certain areas,
forming adipose tissue
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200 µm
© Biophoto Associates/ Photo Researchers, Inc.
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Connective Tissue Proper
• Dense connective tissue
– Contains less ground substance than loose connective tissue
– Dense regular connective tissue
• Collagen fibers line up in parallel
• Makes up tendons and ligaments
– Dense irregular connective tissue
• Collagen fibers have different orientations
• Covers kidney, muscles, nerves, and bone
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Special Connective Tissue
• Cartilage
•
•
•
•
Firm and flexible tissue that does not stretch
Great tensile strength
Found in joint surfaces and other locations
Chondrocytes (cartilage cells) live within lacunae
(spaces) in the ground substance
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Special Connective Tissue
• Bone
– Osteocytes (bone cells) remain alive in a matrix hardened with
calcium phosphate
– Communicate through canaliculi
• Blood
–
–
–
–
Extracellular material is the fluid plasma
Erythrocytes – red blood cells
Leukocytes – white blood cells
Thrombocytes – platelets
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Muscle Tissue
• Muscles are the motors of vertebrate
bodies
• Three kinds: smooth, skeletal, and cardiac
• Skeletal and cardiac muscles are also known as
striated muscles
• Skeletal muscle is under voluntary control,
whereas contraction of the other two is involuntary
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Muscle Tissue
• Smooth muscle
– Found in walls of blood vessels and visceral organs
– Contain a single nucleus
• Skeletal muscle
– Usually attached to bone by tendons, so muscle contraction
causes bones to move
– Muscle fibers (cells) are multinucleated
– Contract by means of myofibrils, which contain ordered actin and
myosin filaments
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Muscle Tissue
• Cardiac muscle
– Composed of smaller, interconnected cells
– Each with a single nucleus
– Interconnections appear as dark lines called
intercalated disks
• Gap junctions link adjacent cells
– Enable cardiac muscle cells to form a single
functioning unit
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Nerve Tissue
• Cells include neurons and
their supporting cells
(neuroglia)
• Most neurons consist of
three parts
– Cell body – contains the
nucleus
– Dendrites – highly branched
extensions
• Conduct electrical impulses
toward the cell body
– Axon – single cytoplasmic
extension
• Conducts impulses away from
cell body
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Nerve Tissue
• Neuroglia
– Do not conduct electrical impulses
– Support and insulate neurons and eliminate
foreign materials in and around neurons
– Associate with axon to form an insulating cover
called the myelin sheath
• Gaps (nodes of Ranvier) are involved in acceleration
of impulses
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Nerve Tissue
• Nervous system is divided
into
– Central nervous system
(CNS)
• Brain and spinal cord
• Integration and interpretation
of input
– Peripheral nervous system
(PNS)
• Nerves and ganglia
(collections of cell bodies)
• Communication of signal to
and from the CNS to the rest
of the body
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Overview of Organ Systems
•
•
•
•
•
Communication and integration
• Three organ systems detect external stimuli and coordinate the
body’s responses:
– Nervous, sensory, and endocrine systems
Support and movement
• Muscle and skeletal systems
Regulation and maintenance
• Four organ systems regulate and maintain the body’s chemistry:
– Digestive, circulatory, respiratory, and urinary systems
Defense
• The body defends itself
– Integumentary and immune systems
Reproduction and development
• Reproductive system
• In females, the system also nurtures the developing embryo and
fetus
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Homeostasis
• As animals have evolved, specialization of
body structures has increased
• For cells to function efficiently and interact
properly, internal body conditions must be
relatively constant
• The dynamic constancy of the internal
environment is called homeostasis
• It is essential for life
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Homeostasis
• Negative feedback mechanisms
• Changing conditions are detected by sensors (cells or membrane receptors)
• Information is fed to an integrating center, also called comparator (brain, spinal
cord, or endocrine gland)
• Compares conditions to a set point
• If conditions deviate too far from a set point, biochemical reactions are initiated to
change conditions back toward the set point
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Homeostasis
• Humans have set points for body temperature, blood
glucose concentrations, electrolyte (ion) concentration,
tendon tension, etc.
• Integrating center is often a particular region of the brain
or spinal cord
• Effectors (muscles or glands) change conditions back
toward the set point values
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Homeostasis
• Mammals and birds are endothermic
– Maintain a relatively constant body temperature independent of
the environmental temperature
– Humans 37oC or 98.6oF
– Changes in body temperature are detected by the hypothalamus
in the brain
• Antagonistic effectors are involved in the control of body
temperature
• If hypothalamus detects high temperature
– Promotes heat dissipation via sweating and dilation of blood
vessels in skin
• If hypothalamus detects low temperature
– Promotes heat conservation via shivering and constriction of
blood vessels in skin
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Homeostasis
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Homeostasis
•
Positive feedback mechanisms
– Enhance a change
• not as common as negative feedback
mechanisms
– These do not in themselves
maintain homeostasis
– Important components of some
physiological mechanisms
• Blood clotting
• Contraction of uterus during
childbirth
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Regulating Body Temperature
• Temperature is one of the most important
aspects of the environment
• Some organisms have a body temperature
that conforms to the environment
• Other organisms regulate their body
temperature
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• Q10 is a measure of temperature sensitivity
– The rate of any chemical reaction is affected
by temperature
– The rate increases with increasing
temperature
– Every 10°C increase in temperature doubles
the reaction rate up to a specific limiting
temperature
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• Temperature determined by internal and
external factors
– Overall metabolic rate and body temperature are
interrelated
– Organisms must deal with external and internal
factors that relate body heat, metabolism, and the
environment
body heat = heat produced + heat transferred
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Mechanisms of heat transfer
• Radiation - The transfer of heat by electromagnetic
radiation
• Conduction - The direct transfer of heat between two
objects. Energy is transferred from hotter objects to
colder ones.
• Convection - Convection is the transfer of heat brought
about by the movement of a gas or liquid.
• Evaporation - Heat of vaporization or the amount of
energy needed to change them from a liquid to a gas
phase
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• Ectotherms regulate temperature using behavior
– Low metabolic rates
– Regulate their temperature using behavior
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Preflight
No wing
movement
Warm up
Shiver-like
contraction
of thorax
muscles
Temperature (ºC) of thorax muscles
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Flight
Full-range
movement
of wings
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30
25
–1
0
1
Time (min)
2
3
4
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• Endotherms create internal metabolic heat
– Conservation or dissipation
– Heat transfer is controlled by amount of blood flow to
the surface of the animal
• Countercurrent exchange
– Allows sustained high-energy activity
– Tradeoff is the high metabolic rate
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• Body size and insulation
– Changes in body mass have a large effect on metabolic rate
– Smaller animals consume much more energy per unit body
mass than larger animals
– Summarized in the “mouse to elephant” curve
• Nonproportionality of metabolic rate versus size of mammals
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• Mammalian thermoregulation is controlled by the
hypothalamus
– Neurons in the hypothalamus detect the temperature
change
– Stimulation of the heat-losing center
• Peripheral blood vessel dilation
• Sweating
– Stimulation of heat-promoting center
•
•
•
•
Thermogenesis – shivering
Constriction of blood peripheral blood vessels
Epinephrine production by adrenal glands
Anterior pituitary produces TSH
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• Why is shivering used to increase
temperature?
• Remember cellular respiration? The conversion of
energy found in glucose molecule into ATP
• Remember that with any energy transformation,
some energy is lost as heat
• If you shiver, your body is forcing the muscles to
go through more cellular respiration, therefore
creating more heat
44
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Perturbing factor
Response
Negative
feedback
Sun
Body temperature
falls
Effector
Stimulus
Body temperature
rises
Stimulus
Body temperature
drops
(
Sensor
Integrating Center
Thermoreceptors
Hypothalamus
(
• Blood vessels dilate
• Glands release sweat
)
Effector
• Blood vessels constrict
• Skeletal muscles
contract, shiver
)
Perturbing factor
Snow and ice
Response
Negative
feedback
Body temperature
rises
Control of body temperature by the hypothalamus
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