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Chapter 42
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The Animal Body and
Principles of Regulation
Chapter 42
Organization of Vertebrate Body
• There are four levels of organization
1.
2.
3.
4.
Cells
Tissues
Organs
Organ systems
• Bodies of vertebrates are composed of
different cell types
– Humans have 210
3
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
4
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
5
Organization of Vertebrate Body
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Cell
Tissue
Organ
Organ System
Cardiac Muscle Cell
Cardiac Muscle
Heart
Circulatory System
6
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
7
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
» Pericardial cavity: Around the heart
» Pleural cavity: Around the lungs
– Abdominopelvic cavity – most organs
» Peritoneal cavity – coelomic space
8
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Section 1
Cranial
cavity
Vertebrae
Section 3
Section 2
Brain
Vertebral
cavity
Spinal
cord
Dorsal
body
cavity
Right pleural
cavity
Pericardial cavity
Thoracic cavity
Diaphragm
Ventral body
cavity
Peritoneal
cavity
a.
All vertebrates have dorsal and ventral body cavities
9
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Section 1
Cranial
cavity
Section 3
Section 2
Brain
Muscles
Mandible
Pharynx
Muscles
Rib
Vertebral
cavity
Pleural
cavity
Epiglottis
Lungs
Sternum
Muscles
Vertebra
Esophagus
Trachea
Anterior
vena cava
Thoracic
cavity
Spleen
Spinal cord
Kidney
Cecum
Colon
Small
intestines
Abdominal
cavity
b.
Cross sections through three body regions
10
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
11
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
12
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
13
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
14
15
Simple Epithelium
• Glands of vertebrates form from
invaginated epithelia
• Exocrine glands
– Connected to epithelium by a duct
– Sweat, sebaceous, and salivary glands
• Endocrine glands
– Ductless – lost duct during development
– Secretions (hormones) enter blood
16
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
17
18
Connective Tissues
• Derive from embryonic mesoderm
• Divided into two major classes
– Connective tissue proper
• Loose or dense
– Special connective tissue
• Cartilage, bone, and blood
• All have abundant extracellular material
called the matrix
– Protein fibers plus ground substance
19
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
20
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.
21
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
22
23
Special Connective Tissue
• Cartilage
– Ground substance made from characteristic
glycoprotein (chondroitin) and collagen fibers
in long, parallel arrays
– 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
24
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
25
26
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
27
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
28
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
29
30
Heartbeat intrinsic to the heart
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Isolated
heart
Heart placed in solution with
nutrients and oxygen.
Heart continues to contract with no connection to the nervous system.
31
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
32
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
33
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
34
35
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
– Musculoskeletal system consists of two
interrelated organ systems
36
Overview of Organ 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
37
Overview of Organ Systems
• Reproduction and development
– The biological continuity of vertebrates
– In females, the system also nurtures the
developing embryo and fetus
38
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Nervous System
Endocrine System
Brain
Hypothalamus
Pituitary
Skeletal System
Skull
Thyroid
Thymus
Spinal
cord
Adrenal
gland
Pancreas
Sternum
Pelvis
Testis
(male)
Nerves
Femur
Ovary (female)
39
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Muscular System
Digestive System
Circulatory System
Salivary
glands
Pectoralis
major
Esophagus
Biceps
Liver
Rectus
abdominus
Stomach
Small
intestine
Large
intestine
Heart
Veins
Arteries
Sartorius
Quadriceps
Gastrocnemius
40
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lymphatic/Immune System
Reproductive System (male)
Reproductive System (female)
Lymph nodes
Thymus
Spleen
Bone marrow
Vas deferens
Penis
Testis
Fallopian
tube
Ovary
Uterus
Vagina
Lymphatic
vessels
41
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lymphatic/Immune System
Reproductive System (male)
Reproductive System (female)
Lymph nodes
Thymus
Spleen
Bone marrow
Vas deferens
Penis
Testis
Fallopian
tube
Ovary
Uterus
Vagina
Lymphatic
vessels
42
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
43
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
44
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 the
value of the condition in question back
toward the set point value
45
Homeostasis
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Response
Move system towards
set point
Effector
Causes changes to
compensate for
deviation
Negative feedback
(–)
Stimulus
Deviation from
set point
Sensor
Integrating Center
Constantly monitors
conditions
Compares conditions
to a set point based
on a desired value
46
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
47
Homeostasis
• Negative feedback mechanisms often
oppose each other to produce finer degree
of control
• Many internal factors are controlled by
antagonistic effectors
• Have “push–pull” action
• Increasing activity of one effector is
accompanied by decrease in the other
48
Homeostasis
• 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
49
Homeostasis
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Negative
feedback
Stimulus
Stimulus
Room temperature
changes from set
point
Body temperature
deviates from
set point
(–)
(–)
Negative
feedback
Negative
feedback
Sensor
Response
Room warms,
temperature
increases
toward set point
Effector
If Below Set Point
• AC turns off
• Furnace turns on
a.
Thermometer in
wall unit detects
the change in
temperature
(–)
(–)
Sensor
Response
Response
Room cools,
temperature
decreases
toward set point
Body
temperature
rises
Neurons in
hypothalamus
detect the change
in temperature
Integrating Center
Integrating Center
Set Point = 70F
Set Point = 37C
Thermostat
compares
temperature
with set point
Negative
feedback
Effector
Effector
If Above Set Point
If Below Set Point
• AC turns on
• Furnace turns off
• Blood vessels to
skin contract
• Muscles contract,
shiver
Neurons in
hypothalamus
compare input
from sensory
neurons with
set point
Response
Body
temperature
drops
Effector
If Above Set Point
• Blood vessels
to skin dilate
• Glands release
sweat
b.
50
Homeostasis
• Positive feedback mechanisms
– Enhance a change – not common
– These do not in themselves maintain
homeostasis
– Important components of some physiological
mechanisms
• Blood clotting
• Contraction of uterus during childbirth
51
Homeostasis
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Stimulus
Fetus is pushed
against the uterine
opening
Sensor
Receptors in the
inferior uterus
detect increased
stretch
Integrating Center
The brain receives
stretch information
from the uterus,
and compares
it with the set point
(+)
Positive feedback
loop completed—
results in increased
force against inferior
uterus (cervix),
promoting the
birth of the baby
Response
Oxytocin causes
increased uterine
contractions
Effector
If Above Set Point
The pituitary gland
is stimulated to
increase secretion of
the hormone oxytocin
52
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53
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
54
• 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
55
• 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
56
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
57
• 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
40
Flight
Full-range
movement
of wings
35
30
25
–1
0
1
Time (min)
2
3
4
58
• 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
59
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Core body
temperature
36°C
5°C
Temperature
of environment
Warm
blood
Cold
blood
Cold
blood
Capillary
bed
Veins
Artery
Countercurrent heat exchange
60
• 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
61
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8
7
Shrew
Mass-specific metabolic rate
(mL O2 × g–1 × h–1)
6
5
4
3
Harvest mouse
2
1
Kangaroo mouse
Cactus mouse
Mouse
Flying squirrel
Cat
Rat
Dog Sheep
Rabbit
0
0.01
0.1
1
10
Human Horse Elephant
100
1000
log Mass (kg)
Relationship between body mass and metabolic rate in mammals
62
• 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
Constriction of blood peripheral blood vessels
Epinephrine production by adrenal glands
Anterior pituitary produces TSH
63
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
64