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Chapter
21
Unifying Concepts of
Animal Structure
and Function
PowerPoint® Lectures created by Edward J. Zalisko for
Campbell Essential Biology, Sixth Edition, and
Campbell Essential Biology with Physiology, Fifth Edition
– Eric J. Simon, Jean L. Dickey, Kelly A. Hogan, and Jane B. Reece
© 2016 Pearson Education, Inc.
Figure 21.0-1
Why Animal Structure and
Function Matter
© 2016 Pearson Education, Inc.
The Structural Organization of Animals
• Life is characterized by a hierarchy of organization.
• In animals,
• individual cells are grouped into tissues,
• tissues combine to form organs,
• organs are organized into organ systems, and
• organ systems make up the entire organism.
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Figure 21.1-s1
Cellular level:
Muscle cell
Tissue level:
Cardiac muscle
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Figure 21.1-s2
Cellular level:
Muscle cell
Tissue level:
Cardiac muscle
Organ level:
Heart
Organ system level:
Circulatory system
© 2016 Pearson Education, Inc.
Figure 21.1-s3
Cellular level:
Muscle cell
Tissue level:
Cardiac muscle
Organ level:
Heart
Organ system level:
Circulatory system
© 2016 Pearson Education, Inc.
Organism level:
Multiple organ
systems
functioning
together
Structure/Function: Anatomy and Physiology
• Biologists distinguish anatomy from physiology.
• Anatomy is the study of the structure of an
organism’s parts.
• Physiology is the study of the function of those
parts.
• The correlation of structure and function is a
fundamental principle of biology that is evident
at all levels of life’s hierarchy.
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Figure 21.2-s1
(a) At the organism
level
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Figure 21.2-s2
(b) At the organ level
(a) At the organism
level
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Figure 21.2-s3
(b) At the organ level
(a) At the organism
level
(c) At the cellular level
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Figure 21.2-1
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Tissues
• The cell is the basic unit of all living organisms.
• In almost all animals, including humans, cells are
grouped into tissues.
• A tissue is an integrated group of similar cells that
performs a specific function.
• Animals have four main categories of tissue:
1. epithelial tissue,
2. connective tissue,
3. muscle tissue, and
4. nervous tissue.
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Epithelial Tissue
• Epithelial tissue, also known as epithelium,
• covers the surface of the body and
• lines organs.
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Figure 21.3
Examples of organs
lined with epithelial
tissue
Heart
Lung
Stomach
Small intestine
Large intestine
Urinary bladder
Epithelial
Epithelial tissue
covering body (skin) cells
Spaces for
exchange
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Epithelial tissue
lining capillaries
Epithelial Tissue
• The body continuously renews the cells of many
epithelial tissues.
• Such turnover requires cells to divide rapidly, which
increases the risk of an error in cell division, a
mistake that can lead to cancer.
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Connective Tissue
• Connective tissue contains cells scattered
throughout a material called the extracellular
matrix.
• The structure of the matrix varies and matches the
function of each tissue.
• Two major functions of the connective tissue are to
support and join other tissues.
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Figure 21.4
Loose connective
tissue
Adipose
tissue
Blood
Fibrous
connective
tissue
Bone
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Cartilage
Figure 21.4-1
Cell
Collagen
fiber
Loose connective tissue
(under the skin)
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Figure 21.4-2
Fat
droplets
Adipose tissue
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Figure 21.4-3
White blood
cells
Red blood
cell
Plasma
Blood
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Figure 21.4-4
Cell
nucleus
Collagen
fibers
Fibrous connective tissue
(forming a tendon)
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Figure 21.4-5
Cells
Matrix
Cartilage
(at the end of a bone)
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Figure 21.4-6
Matrix
Cells
Bone
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Connective Tissue
• Figure 21.4 illustrates six of the major types of
connective tissue.
1. Loose connective tissue
• is the most widespread connective tissue in the
body of vertebrates and
• binds epithelia to underlying tissues.
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Connective Tissue
2. Fibrous connective tissue has a dense matrix
of collagen. It forms
• tendons, which attach muscles to bones, and
• ligaments, which strongly join bones together at
joints.
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Connective Tissue
3. Cartilage
• is strong but flexible,
• has no blood vessels, so it heals very slowly, and
• functions as a flexible, boneless skeleton.
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Connective Tissue
4. Bone
• is a rigid connective tissue with a matrix of collagen
fibers hardened with deposits of calcium salts.
• This combination makes bone hard without being
brittle.
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Connective Tissue
5. Adipose tissue
• stores fat in closely packed cells of a sparse matrix,
• functions as an energy bank, and
• insulates and cushions the body.
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Connective Tissue
6. Blood
• consists of cells suspended in a liquid matrix called
plasma and
• transports substances in the plasma from one part
of the body to another,
• plays major roles in immunity, and
• seals broken blood vessels.
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Muscle Tissue
• Muscle tissue
• is the most abundant tissue in most animals,
• consists of bundles of long, thin, cylindrical cells
called muscle fibers, and
• has specialized proteins arranged into a structure
that contracts when stimulated by a signal from a
nerve.
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Figure 21.5
Skeletal muscle
Cardiac muscle
Smooth muscle
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Figure 21.5-1
Unit of
muscle
contraction
Muscle
fiber
(cell)
Nuclei
Skeletal muscle
(short segments of
several muscle fibers)
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Figure 21.5-2
Junction between
two cells
Muscle
fiber
Nucleus
Cardiac muscle
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Figure 21.5-3
Muscle fiber
Nucleus
Smooth muscle
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Muscle Tissue
• Skeletal muscle
• is attached to bones by tendons,
• moves your skeleton, and
• is responsible for voluntary movements.
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Muscle Tissue
• Cardiac muscle is found only in heart tissue.
The contraction of the cardiac muscle produces
a coordinated heartbeat.
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Muscle Tissue
• Smooth muscle is found in many organs and
can contract slowly for a long period of time.
• The powerful contractions of smooth muscle
expel the fetus from the uterus during childbirth.
• The walls of the intestines are composed of
smooth muscle that contracts to move food and
waste along.
• Smooth muscle is also found in blood vessels.
Rings of smooth muscle in blood vessels widen,
causing blood to quickly flow to your face and
neck.
© 2016 Pearson Education, Inc.
Nervous Tissue
• Nervous tissue
• makes communication of information possible,
• is found in your brain and spinal cord, and
• consists of a network of neurons.
• The basic unit of nervous tissue is the neuron,
or nerve cell.
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Figure 21.6
Brain
Signal-receiving
extensions
Cell body
Nerve
LM
Signaltransmitting
extension
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Spinal cord
Figure 21.6-1
Signal-receiving
Cell body
extensions
LM
Signaltransmitting
extension
© 2016 Pearson Education, Inc.
Interconnections within Systems: Organs and
Organ Systems
• An organ consists of two or more tissues
packaged into one working unit that performs a
specific function.
• An organ performs functions that none of its
component tissues can carry out alone.
• Examples include the heart, brain, and small
intestines.
• To see how multiple tissues interconnect in a single
organ, examine the layered arrangement of tissues
in the wall of the small intestine in Figure 21.7.
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Figure 21.7
Small intestine
(cut open)
Epithelial tissue
Connective tissue
(containing blood
and lymph vessels)
Smooth muscle
tissue (two layers)
Connective tissue
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Epithelial
tissue
Interconnections within Systems: Organs and
Organ Systems
• Organ systems are teams of organs that
• work together and
• perform vital body functions.
© 2016 Pearson Education, Inc.
Figure 21.8-1
Metacarpals
Carpals
Radius
Ulna
Humerus
Shoulder
Clavicle
girdle
Scapula
Phalanges
Skull
Bone
Sternum
Ribs
Vertebra
Cartilage
Pelvic girdle
Skeletal system:
supports body and
anchors muscles
Femur
Patella
Tibia
Fibula
Tarsals
Metatarsals
Phalanges
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Figure 21.8-2
Circulatory system:
transports substances
throughout body
Heart
Blood
vessels
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Figure 21.8-3
Nasal cavity
Pharynx
Respiratory system:
exchanges O2 and
CO2 between blood
and air
Larynx
Trachea
Bronchus
Lung
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Figure 21.8-4
Muscular system:
moves the body
Skeletal muscles
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Figure 21.8-5
Digestive system:
breaks down food
and absorbs
nutrients
Mouth
Esophagus
Liver
Stomach
Large intestine
Small intestine
Anus
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Figure 21.8-6
Urinary system:
rids body of
certain wastes
Kidney
Ureter
Urinary bladder
Urethra
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Figure 21.8-7
Endocrine system:
secretes hormones
that regulate body
Hypothalamus
Pituitary gland
Parathyroid gland
Thyroid gland
Adrenal gland
Pancreas
Testis (male)
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Ovary
(female)
Figure 21.8-8
Reproductive system:
produces gametes
and offspring
Seminal vesicles
Prostate gland
Oviduct
Vas deferens
Ovary
Uterus
Vagina
Penis
Urethra
Testis
© 2016 Pearson Education, Inc.
Figure 21.8-9
Integumentary
system:
protects body
Hair
Skin
Nail
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Figure 21.8-10
Lymphatic and
immune system:
defends against
disease
Tonsil
Thymus
Spleen
Appendix
Lymph nodes
Lymphatic
vessels
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Figure 21.8-11
Nervous system:
processes sensory
information
and controls
responses
Brain
Sense organ
(ear)
Spinal cord
Nerves
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Interconnections within Systems: Organs and
Organ Systems
• An organism depends on the interconnection of all
its organ systems for survival.
• Your body is a whole, living unit that is greater than
the sum of its parts.
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Exchanges with the External Environment
• Every organism is an open system that
continuously exchanges chemicals and energy
with its surroundings.
• An animal’s size and shape affect its exchanges
with its surrounding environment.
• Every living cell of an animal’s body must be
bathed in a watery solution, partly because
substances must be dissolved in water to cross
cell membranes.
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Exchanges with the External Environment
• In a single-celled amoeba, every part of the cell’s
membrane touches the outside world, where
exchange with the watery environment can occur.
• A hydra has a body wall only two cell layers thick.
• Both layers of cells are bathed in pond water, which
enters the digestive sac through the mouth.
• Every cell of the hydra can thus exchange materials
through direct contact with the aqueous
environment.
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Figure 21.9
Mouth
Gastrovascular
cavity
Exchange
Exchange
Exchange
(a) Single cell
(b) Two cell layers
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Figure 21.9-1
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Exchanges with the External Environment
• Exchange with the environment is more
complicated for complex, multilayered animals.
• Each cell in a multicellular organism has a plasma
membrane where exchange can occur.
• But this exchange only works if all the cells of the
animal have access to a suitable watery
environment.
© 2016 Pearson Education, Inc.
Exchanges with the External Environment
• Figure 21.10 shows a schematic model of an
animal body, highlighting the three organ systems
(digestive, respiratory, and urinary) that exchange
materials with the external environment.
• The circulatory system connects to nearly every
organ system as it
• transports needed materials from the environment
to the body’s tissues and
• carries wastes away.
© 2016 Pearson Education, Inc.
Figure 21.10
External environment
CO2 O
Food
2
Mouth
Animal
Respiratory
system
Digestive
system
Interstitial
fluid
Heart
Nutrients
Circulatory
system
Body cells
Urinary
system
Anus
Unabsorbed matter
(feces)
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Metabolic waste products
(such as urine)
Exchanges with the External Environment
• Complex animals have evolved extensively folded
or branched internal surfaces that maximize
surface area for exchange with the immediate
environment.
• Lungs exchange oxygen and carbon dioxide with
the air you breathe.
• The epithelium of the lungs has a very large total
surface area.
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Figure 21.11
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Regulating The Internal Environment
• Animals adjust to a changing environment.
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Homeostasis
• The internal environment of vertebrates includes
the interstitial fluid that
• fills the spaces between cells and
• exchanges nutrients and wastes with microscopic
blood vessels.
• Homeostasis, which literally means “steady state,”
is the tendency to maintain relatively constant
conditions in the internal environment even when
the external environment changes.
© 2016 Pearson Education, Inc.
Figure 21.12
Animal’s internal
environment
External
environment
37C
HOMEOSTATIC
MECHANISMS
39C
38C
4C
Large external changes
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Small internal changes
Thermoregulation
• The homeostatic mechanism that controls
temperature is called thermoregulation.
• The ability to maintain a body temperature
substantially warmer than the surrounding
environment is characteristic of endotherms,
animals such as mammals and birds that derive
most of their body heat from their own metabolism.
• In contrast, ectotherms, which include most
invertebrates, fishes, amphibians, and nonbird
reptiles, obtain their body heat primarily by
absorbing it from their surroundings.
© 2016 Pearson Education, Inc.
Thermoregulation
• You have a number of structures and mechanisms
that aid in thermoregulation.
• When your body temperature falls below normal,
your brain’s control center sends signals that trigger
changes that will bring it back to normal.
• Blood vessels near your body’s surface constrict
(reducing heat loss from your body surface) and
muscles contract, causing you to shiver.
• When body temperature gets too high, the control
center sends signals to dilate the blood vessels near
your skin and activate sweat glands, allowing
excess heat to escape.
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Thermoregulation
• Fever, an abnormally high internal temperature is
a body-wide response that usually indicates an
ongoing fight against infection.
• Many people mistakenly believe that the invading
microbes themselves cause a fever. In fact, the
cause is usually the body’s fight against the
microbes.
• A moderate fever of 38–39°C (100–102°F),
however, discourages bacterial growth and speeds
the body’s internal defenses.
© 2016 Pearson Education, Inc.
Figure 21.14
Skin
Sweat
gland
Response:
1. Blood
vessels dilate
2. Sweat is
produced
Control center
in brain activates
cooling mechanisms
Stimulus:
Body
temperature
is above
set point
Body
temperature
drops
Set point:
Body temperature near 37C (98.6F)
Body
temperature
rises
Skin
© 2016 Pearson Education, Inc.
Stimulus:
Body
temperature
is below
set point
Response:
1. Blood vessels
constrict
2. Person shivers
3. Metabolic rate increases
Control center
in brain activates
warming mechanisms
Figure 21.14-1
Skin
Sweat
gland
Response:
1. Blood
vessels
dilate
2. Sweat is
produced
Stimulus:
Body
temperature
is above
set point
Body
temperature
drops
Set point:
Body temperature near 37C (98.6F)
© 2016 Pearson Education, Inc.
Control
center in
brain activates
cooling
mechanisms
Figure 21.14-2
Set point:
Body temperature near 37C (98.6F)
Stimulus:
Body
temperature
is below
set point
Body
temperature
rises
Skin
© 2016 Pearson Education, Inc.
Response:
1. Blood vessels
constrict
2. Person shivers
3. Metabolic rate
increases
Control center
in brain activates
warming
mechanisms
The Process of Science: How Does a Python
Warm Her Eggs?
• Observation: A female Burmese python incubating
her eggs
• wraps her body around them and
• frequently contracts the muscles in her coils.
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The Process of Science: How Does a Python
Warm Her Eggs?
• Hypothesis: The snake’s muscle contractions
elevate its body temperature for transfer of heat
to its eggs.
• Experiment:
• Researchers placed a python and her eggs in a
chamber and varied the chamber’s temperature.
• They monitored the rate of the python’s muscle
contractions and took into account the snake’s
oxygen uptake, a measure of the rate of cellular
respiration.
© 2016 Pearson Education, Inc.
The Process of Science: How Does a Python
Warm Her Eggs?
• Results: The python’s oxygen consumption
increased when the temperature in the chamber
decreased.
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O2 consumption (mL O2/hr) per kg
Figure 21.15
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120
100
80
60
40
20
0
5
10
15
20
25
30
Contractions per minute
35
Osmoregulation
• Living cells depend on a precise balance of
• water and
• solutes.
• Osmoregulation is the control of the gain or
loss of
• water and
• dissolved solutes, such as the ions of NaCl and
other salts.
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Osmoregulation
• Saltwater fish lose water by osmosis because there
is less salt in their tissues than the water they swim
in.
• Freshwater fish have the opposite problem:
The external solute concentration is low, so water
enters the fish by osmosis.
• Most land animals lose water through urinating,
defecating, breathing, and perspiring but can
counterbalance the loss by eating and drinking
© 2016 Pearson Education, Inc.
Figure 21.16
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Interconnections within Systems: Homeostasis
in the Urinary System
• The urinary system plays a central role in
osmoregulation, regulating the amount of water
and solutes in body fluids by retaining water when
we are dehydrated and expelling it when we are
hydrated.
• Besides osmoregulation, the urinary system plays
another important role—the excretion of wastes.
© 2016 Pearson Education, Inc.
Interconnections within Systems: Homeostasis
in the Urinary System
• In humans, the two kidneys
• are the main processing centers and
• contain nearly 100 miles of thin tubes called
tubules and an intricate network of capillaries.
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Interconnections within Systems: Homeostasis
in the Urinary System
• As blood circulates through the kidneys, a fraction
of it is filtered and plasma enters the kidney
tubules, forming filtrate.
• Filtrate contains
• valuable substances that need to be reclaimed
(such as water and glucose) and
• substances to be eliminated, such as urea.
© 2016 Pearson Education, Inc.
Interconnections within Systems: Homeostasis
in the Urinary System
• The human urinary system includes
• the circulatory system,
• the kidneys,
• nephrons, the functional units within the kidneys,
and
• the urinary bladder, where urine is stored.
© 2016 Pearson Education, Inc.
Figure 21.17
Filter
Tubule
Renal artery
(red) and
renal vein
(blue)
Branch
of renal
artery
Collecting
duct
Branch of
renal vein
Kidney
Ureter
Urinary bladder
Ureter
Urethra
(b) Kidney
(cutaway view)
(a) Urinary system
© 2016 Pearson Education, Inc.
To ureter
(c) Blood supply
to a nephron
Figure 21.17-1
Renal artery
(red) and
renal vein
(blue)
Kidney
Ureter
Urinary bladder
Urethra
(a) Urinary system
© 2016 Pearson Education, Inc.
Figure 21.17-2
Filter
Tubule
Branch
of renal
artery
Collecting
duct
Branch of
renal vein
To ureter
Ureter
(b) Kidney (cutaway view)
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(c) Blood supply to a nephron
Interconnections within Systems: Homeostasis
in the Urinary System
• Nephrons
• carry out the functions of the urinary system,
• consist of a tubule and its associated blood
vessels, and
• number more than a million in a kidney.
© 2016 Pearson Education, Inc.
Interconnections within Systems: Homeostasis
in the Urinary System
• Nephrons perform four key functions:
1. Filtration occurs as water and other small
molecules are forced out of the blood when it
passes through capillary walls into the kidney
tubule, forming filtrate.
2. Reabsorption reclaims water and valuable
solutes from the filtrate and returns them to the
blood.
3. Secretion of certain substances, such as some
ions and drugs, that are transported into the
filtrate.
4. Excretion of urine from the kidneys to the
outside.
© 2016 Pearson Education, Inc.
Figure 21.18
Filtration
Renal
artery
Filtrate
Reabsorption
Renal vein
Secretion
Capillaries
Tubule
Excretion
© 2016 Pearson Education, Inc.
Urine
Interconnections within Systems: Homeostasis
in the Urinary System
• Hormones regulate the kidney’s nephrons to
maintain water balance and are central to the
interconnections of the nervous, endocrine,
and urinary systems.
© 2016 Pearson Education, Inc.
Interconnections within Systems: Homeostasis
in the Urinary System
• Understanding filtration, reabsorption, and
secretion will help you see why urine samples are
often used to assess health.
• The presence of glucose in a urine sample suggests
diabetes, a serious condition in which the blood
glucose level is elevated.
• Drugs are secreted into urine and can be detected
there.
• Pregnancy can be confirmed by the presence of a
specific hormone excreted only in the urine of
pregnant women.
© 2016 Pearson Education, Inc.
Interconnections within Systems: Homeostasis
in the Urinary System
• Factors affecting urine composition include
• the environment,
• presence of disease,
• secretions from the various harmless microbes
that can live in the lower part of the urethra, and
• diet.
© 2016 Pearson Education, Inc.
Figure 21.19
© 2016 Pearson Education, Inc.
Evolution Connection: Adaptations for
Thermoregulation
• Natural selection has promoted a wide variety
of adaptations for thermoregulation including
anatomical, physiological, and behavioral
adaptations.
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Evolution Connection: Adaptations for
Thermoregulation
• A major anatomical adaptation in mammals and
birds is insulation, consisting of
• hair (fur),
• feathers, or
• fat layers.
© 2016 Pearson Education, Inc.
Evolution Connection: Adaptations for
Thermoregulation
• Some adaptations are physiological, such as
• land mammals and birds reacting to cold by raising
their fur or feathers,
• hormonal changes tending to boost the metabolic
rate of some birds and mammals, increasing their
heat production in cold weather,
• shivering to produce heat as a metabolic by-product
of the contraction of skeletal muscles, and
• panting and sweating to greatly increase cooling.
© 2016 Pearson Education, Inc.
Figure 21.20
METHODS OF THERMOREGULATION
Anatomical Adaptations
(such as hair, fat,
and feathers)
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Behavioral Adaptations
Physiological Adaptations
(such as panting, shivering, (such as bathing, basking,
hibernating, and migrating)
and sweating)
Figure 21.20-1
Anatomical Adaptations
(such as hair, fat, and feathers)
© 2016 Pearson Education, Inc.
Figure 21.20-2
Physiological Adaptations
(such as panting, shivering,
and sweating)
© 2016 Pearson Education, Inc.
Figure 21.20-3
Behavioral Adaptations
(such as bathing, basking,
hibernating, and migrating)
© 2016 Pearson Education, Inc.
Figure 21.20-4
© 2016 Pearson Education, Inc.
Evolution Connection: Adaptations for
Thermoregulation
• A variety of behavioral responses can regulate
body temperature.
• Some birds and butterflies migrate seasonally to
more suitable climates.
• Other animals, such as desert lizards, bask in the
sun when it is cold and find cool, damp areas or
burrows when it is hot.
• Emperor penguins huddle together to stay warm.
• Many animals cool themselves by bathing.
© 2016 Pearson Education, Inc.
Figure 21.UN01
HIERARCHICAL ORGANIZATION OF ANIMALS
Level
Description
Cell
The basic unit of
all living organisms
Example
Muscle cell
Tissue
A collection of similar
cells performing
a specific function
Cardiac muscle
Organ
Multiple tissues
forming a structure
that performs a
specific function
Heart
Organ system
A team of organs
that work together
Circulatory system
Organism
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A living being, which
depends on the
coordination of all
structural levels for
homeostasis and
survival
Person
Figure 21.UN01a
HIERARCHICAL ORGANIZATION OF ANIMALS
Level
Description
Cell
The basic unit of
all living organisms
Example
Muscle cell
Tissue
A collection of similar
cells performing
a specific function
Cardiac muscle
Organ
Multiple tissues
forming a structure
that performs a
specific function
Heart
© 2016 Pearson Education, Inc.
Figure 21.UN01b
HIERARCHICAL ORGANIZATION OF ANIMALS
Level
Description
Organ system
A team of organs
that work together
Example
Circulatory system
Organism
© 2016 Pearson Education, Inc.
A living being, which
depends on the
coordination of all
structural levels for
homeostasis and
survival
Person
Figure 21.UN02
Muscle (contracts)
Connective
(supports organs)
Epithelial (covers
body surfaces and
organs)
© 2016 Pearson Education, Inc.
Nervous (relays
and integrates
information)
Figure 21.UN03
Blood
Capillaries
Tubule
Filtration
Water and small
molecules enter
the tubule.
Reabsorption
Water and valuable
solutes are returned
to the blood.
Secretion
Specific substances
are removed from
the blood.
Urine
© 2016 Pearson Education, Inc.
Excretion
Urine exits the body.
Figure 21.UN04
Body temperature (C)
40
River otter
30
20
Largemouth
bass
10
0
0
10
20
30
Ambient (environmental)
temperature (C)
© 2016 Pearson Education, Inc.
40