The document discusses the hierarchical organization of animals from the cellular level to the organism level. Cells combine to form tissues, tissues combine to form organs, organs work together in organ systems, and organ systems function together to form the whole organism. The key levels of organization are the cell, tissue, organ, organ system, and organism. The four main tissue types are epithelial, connective, muscle and nervous tissue. Organ systems include the circulatory, respiratory, digestive and others that work to exchange materials and regulate the internal environment.

1. © 2010 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
– Organ systems make up the entire organism

2. Cellular level:
Muscle cell
Figure 21.1-1

3. Cellular level:
Muscle cell
Tissue level:
Cardiac muscle
Figure 21.1-2

4. Cellular level:
Muscle cell
Tissue level:
Cardiac muscle
Organ level:
Heart
Figure 21.1-3

5. Cellular level:
Muscle cell
Tissue level:
Cardiac muscle
Organ level:
Heart
Organ system level:
Circulatory system Organism level: Multiple
organ systems
functioning together
Figure 21.1-5

6. © 2010 Pearson Education, Inc.
Cell
Level Description
The basic unit of
all living organisms
Muscle cell
Example
HIERARCHICAL ORGANIZATION OF ANIMALS
Figure 21.UN01a

7. © 2010 Pearson Education, Inc.
Level Description Example
HIERARCHICAL ORGANIZATION OF ANIMALS
Tissue A collection of similar
cells that perform
a specific function
Cardiac muscle
Figure 21.UN01b

8. © 2010 Pearson Education, Inc.
Level Description Example
HIERARCHICAL ORGANIZATION OF ANIMALS
Organ Multiple tissues
forming a structure
that performs a
specific function
Heart
Figure 21.UN01c

9. © 2010 Pearson Education, Inc.
Level Description Example
HIERARCHICAL ORGANIZATION OF ANIMALS
Organ
system
A team of organs that
work together
Circulatory
system
Figure 21.UN01d

10. © 2010 Pearson Education, Inc.
Level Description Example
HIERARCHICAL ORGANIZATION OF ANIMALS
Organism A living being, which
depends on the
coordination of all
structural levels for
homeostasis and
survival Person
Figure 21.UN01e

11. © 2010 Pearson Education, Inc.
Cell
Level
Tissue
Organ
Organ system
Organism
Description
The basic unit of
all living organisms
A collection of similar
cells that perform
a specific function
Multiple tissues
forming a structure
that performs a
specific function
A team of organs that
work together
A living being, which
depends on the coordination
of all structural levels for
homeostasis and survival
Muscle cell
Example
Cardiac muscle
Heart
Circulatory system
Person
HIERARCHICAL ORGANIZATION OF ANIMALS
Figure 21.UN01

12. © 2010 Pearson Education, Inc.
Form Fits Function
• Analyzing a biological structure gives us clues about:
– What it does
– How it works

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• Biologists distinguish anatomy from physiology.
– Anatomy is the study of the structure of an organism.
– Physiology is the study of the function of an organism’s structural
equipment.

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Tissues
• In most multicellular animals, cells are grouped into tissues.
– A tissue is an integrated group of similar cells that perform a specific
function.
– Animals have four main categories of tissue.

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Epithelial Tissue
• Epithelial tissue, also known as epithelium:
– Covers the surface of the body
– Lines organs and cavities within the body

16. Some examples of organs
lined with epithelial tissue:
Heart
Lung
Stomach
Small intestine
Large intestine
Urinary bladder
Figure 21.3a

17. Epithelial tissue lining esophagus
Figure 21.3b

18. Epithelial tissue lining small intestine
Figure 21.3c

19. © 2010 Pearson Education, Inc.
• Cells of epithelial tissues:
– Are bound tightly together
– Form a protective barrier
– Fall off and are continuously renewed

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Connective Tissue
• Connective tissues have a sparse population of cells in an
extracellular matrix consisting of a web of protein fibers within a
uniform foundation that may be liquid, jellylike, or solid.
• The structure of connective tissue is correlated with its function:
to bind and support other tissues.

21. (a) Loose connective tissue
(under the skin)
(b) Adipose tissue
(c) Blood
(d) Fibrous connective tissue
(forming a tendon)
(e) Cartilage (at the end of a bone)
(f) Bone
Cell
Cells
Matrix
Plasma
Matrix
Cells
Collagen
fiber
Fat
droplets
White blood
cells
Red blood
cell
Cell
nucleus
Collagen
fibers
Figure 21.4

22. © 2010 Pearson Education, Inc.
• Loose connective tissue:
– Is the most widespread connective tissue
– Binds epithelia to underlying tissues
– Holds organs in place

23. (a) Loose connective tissue
(under the skin)
Cell
Collagen fiber
Figure 21.4a

24. © 2010 Pearson Education, Inc.
• Adipose tissue:
– Stores fat
– Stockpiles energy
– Pads and insulates the body

25. (b) Adipose tissue
Fat
droplets
Figure 21.4b

26. © 2010 Pearson Education, Inc.
• Blood:
– Is a connective tissue with a matrix of liquid
– Contains red and white blood cells suspended in plasma

27. (c) Blood
Plasma
White blood cells
Red blood cell
Figure 21.4c

28. © 2010 Pearson Education, Inc.
• Fibrous connective tissue:
– Has a dense matrix of collagen
– Forms tendons and ligaments

29. (d) Fibrous connective tissue
(forming a tendon)
Cell nucleus
Collagen fibers
Figure 21.4d

30. © 2010 Pearson Education, Inc.
• Cartilage:
– Has a strong but rubbery matrix
– Functions as a flexible, boneless skeleton
– Forms the shock-absorbing pads that cushion the vertebrae of the spinal
column

31. (e) Cartilage (at the end of a bone)
Matrix
Cells
Figure 21.4e

32. © 2010 Pearson Education, Inc.
• Bone:
– Is a rigid connective tissue
– Has a matrix of collagen fibers hardened with deposits of calcium salts

33. (f) Bone
Cells
Matrix
Figure 21.4f

34. © 2010 Pearson Education, Inc.
Muscle Tissue
• Muscle tissue:
– Consists of bundles of long, thin, cylindrical cells called muscle fibers
– Has specialized proteins that contract when stimulated by a nerve

35. (a) Skeletal muscle
(short segments of
several muscle fibers)
(b) Cardiac muscle
Unit of
muscle
contraction
Muscle
fiber
(cell)
Muscle
fiber
Junction between
two cells
(c) Smooth muscle
Nucleus
Nucleus
Muscle fiber
Nuclei
Figure 21.5

36. (a) Skeletal muscle
(short segments of
several muscle fibers)
Unit of
muscle
contraction
Muscle fiber
(cell)
Nuclei
Figure 21.5a

37. (b) Cardiac muscle
Muscle
fiber
Junction between two cells
Nucleus
Figure 21.5b

38. (c) Smooth muscle
Muscle fiber
Nucleus
Figure 21.5c

39. © 2010 Pearson Education, Inc.
• Skeletal muscle is:
– Attached to bones by tendons
– Responsible for voluntary movements
– Striated because the contractile apparatus forms a banded pattern in each
cell or fiber

40. © 2010 Pearson Education, Inc.
• Cardiac muscle is:
– Composed of cells that are branched and striated
– Found only in heart tissue
– Responsible for the contraction of the heart

41. © 2010 Pearson Education, Inc.
• Smooth muscle is:
– Named for its lack of obvious striations
– Found in the walls of various organs
– Involuntary

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Nervous Tissue
• Nervous tissue:
– Makes communication of sensory information possible
– Is found in the brain and spinal cord
– Consists of a network of neurons

43. Brain
Nerve
Spinal cord
Figure 21.6a

44. Signal-receiving
extensions Cell body
Signal-
transmitting
extensions
LM
Figure 21.6b

45. © 2010 Pearson Education, Inc.
Organs and Organ Systems
• An organ consists of two or more tissues packaged into one
working unit that performs a specific function.
• Examples include the heart, liver, stomach, brain, and lungs.

46. © 2010 Pearson Education, Inc.
• Organ systems:
– Are teams of organs that work together
– Perform vital body functions
Blast Animation: Anatomy of the Kidney

47. Skeletal system:
supports body and
anchors muscles
Cartilage
Bone
Figure 21.8a

48. Circulatory system:
transports substances
throughout body
Blood vessels
Heart
Figure 21.8b

49. Respiratory system:
exchanges O2 and
CO2 between blood
and air
Nasal cavity
Bronchus
Pharynx
Trachea
Larynx
Lung
Figure 21.8c

50. Digestive system:
breaks down food
and absorbs
nutrients
Large intestine
Small intestine
Esophagus
Stomach
Liver
Mouth
Anus
Figure 21.8e

51. Muscular system:
moves body
Skeletal muscles
Figure 21.8d

52. Urinary system:
rids body of
certain wastes
Urinary bladder
Urethra
Ureter
Kidney
Figure 21.8f

53. Reproductive system:
produces gametes
and offspring
Seminal vesicles
Prostate gland
Vas deferens
Urethra
Oviduct
Vagina
Uterus
Ovary Penis
Testis
Figure 21.8h

54. Lymphatic and
immune system:
defends against
disease
Lymphatic
vessels
Lymph
nodes
Thymus
Spleen
Figure 21.8j

55. Sense organ
(ear)
Nervous system:
processes sensory
information
and controls
responses Spinal cord
Nerves
Brain
Figure 21.8k

56. © 2010 Pearson Education, Inc.
EXCHANGES WITH THE EXTERNAL
ENVIRONMENT
• Every organism is an open system, continuously exchanging
chemicals and energy with its surroundings to survive.

57. © 2010 Pearson Education, Inc.
• An animal’s size and shape affect how it exchanges energy and
materials with its surroundings.
• All living cells must be bathed in a watery solution so that
exchange of materials can occur.

58. © 2010 Pearson Education, Inc.
• Animals use three organ systems to exchange materials with the
external environment:
– Digestive
– Respiratory
– Urinary
• The circulatory system transports materials inside the body from
these exchange surfaces.

59. Unabsorbed matter (feces) Metabolic waste products (such as urine)
External environment
Respiratory
systemDigestive
system
Urinary
system
Circulatory
system
Interstitial
fluid
Nutrients
Body cells
Animal
Mouth Food
Anus
Heart
CO2
O2
Figure 21.11

60. © 2010 Pearson Education, Inc.
REGULATING THE INTERNAL
ENVIRONMENT
• Every living organism has the ability to respond to its
environment.

61. © 2010 Pearson Education, Inc.
Homeostasis
• Homeostasis is the body’s tendency to maintain relatively steady
conditions in the internal environment when the external
environment changes.

62. External
environment
Large external
changes
Animal’s internal
environment
Homeostatic
mechanisms
Small internal
changes
Figure 21.12

63. © 2010 Pearson Education, Inc.
Negative and Positive Feedback
• Most mechanisms of homeostasis depend on a common principle
called negative feedback, in which the results of a process inhibit
that same process, such as a thermostat that turns off a heater
when room temperature rises to the set point.
Animation: Positive Feedback
Animation: Negative Feedback

64. Thermostat
(control center)
turns heater off
Set point:
Room temperature
20C (68F)
Room
temperature
drops
Response:
Heating
stops
Stimulus:
Room temperature
is above set point
Figure 21.13a

65. Thermostat
(control center)
turns heater on
Set point:
Room temperature
20C (68F)
Room
temperature
rises
Response:
Heating
starts
Stimulus:
Room temperature
is below set point
Figure 21.13b

66. © 2010 Pearson Education, Inc.
• Less common is positive feedback in which the results of a
process intensify that same process, such as uterine contractions
during childbirth.

67. © 2010 Pearson Education, Inc.
• Humans have homeostatic mechanisms that aid in
thermoregulation, which:
– Cool or
– Heat the body
Blast Animation: Negative Feedback: Body Temperature

68. Body
temperature
drops
Set point:
Body temperature near 37C (98.6F)
Stimulus:
Body temperature
is above set point
Control center
in brain activates
cooling mechanisms
Response:
1. Blood
vessels
dilate
2. Sweat is
produced
Sweat
gland
Skin
Figure 21.14a

69. Set point:
Body temperature near 37C (98.6F)
Body
temperature
rises
Stimulus:
Body temperature
is below set point
Control center
in brain activates
warming mechanisms
Response:
1. Blood vessels
constrict
2. Muscles shiver
3. Metabolic rate
increases
Skin
Figure 21.14b

70. © 2010 Pearson Education, Inc.
• Fever:
– Is an abnormally high internal body temperature
– Usually indicates an ongoing fight against infection

71. © 2010 Pearson Education, Inc.
Osmoregulation
• Living cells depend on a precise balance of:
– Water
– Solutes
• Osmoregulation is the control of the gain or loss of:
– Water
– Dissolved solutes, such as salt

72. © 2010 Pearson Education, Inc.
Homeostasis in the Urinary System
• The urinary system:
– Plays a central role in homeostasis
– Forms and excretes urine
– Regulates the amount of water and solutes in body fluids

73. © 2010 Pearson Education, Inc.
• In humans, the two kidneys:
– Are the main processing centers
– Contain many fine tubes called tubules
– Include an intricate network of capillaries

74. © 2010 Pearson Education, Inc.
• As blood circulates through the kidneys:
– A fraction of it is filtered
– Plasma enters the kidney tubules, forming filtrate
• Filtrate contains:
– Valuable substances that need to be reclaimed (such as water and
glucose)
– Substances to be eliminated, such as urea

75. © 2010 Pearson Education, Inc.
• The human urinary system includes:
– The kidneys
– Nephrons, the functional units of the kidney
– The urinary bladder, where urine is stored
Animation: Nephron Introduction

76. Renal artery (red) and
renal vein (blue)
(a) Urinary system
Kidney
Ureter
Urinary
bladder
Urethra
Figure 21.17a

77. (b) Kidney
Ureter
Nephron
Figure 21.17b

78. © 2010 Pearson Education, Inc.
• Nephrons:
– Carry out the functions of the urinary system
– Consist of a tubule and its associated vessels
– Number more than a million in a kidney

79. (c) A nephron and collecting duct
Branch of
renal artery
Branch of
renal vein Collecting
duct
Filter Tubule
To ureter
Figure 21.17c

80. © 2010 Pearson Education, Inc.
• Nephrons perform four key functions:
– Filtration, forcing water and other small molecules from the blood to
form filtrate
– Reabsorption of water and valuable solutes back into the blood
– Secretion of certain substances, such as ions and drugs, into the filtrate
– Excretion of urine from the kidneys

81. Filtration Reabsorption Secretion
Renal artery
Renal vein
Capillaries
Tubule
Urine
Filtrate
Excretion
Figure 21.18

82. © 2010 Pearson Education, Inc.
• Hormonal control of the nephrons allows the body to control its
internal concentration of:
– Water
– Dissolved molecules

83. © 2010 Pearson Education, Inc.
• Kidney failure can be caused by:
– Injury
– Illness
– Prolonged use of pain relievers, alcohol, or other drugs
• One option for treatment of kidney failure is dialysis, filtration of
blood by a machine.

84. Used dialyzing
solution (with
urea and
excess salts)
Line from
apparatus
to vein
Fresh dialyzing
solution
Dialyzing
solution
Line from artery
to apparatus
Tubing made of a
selectively permeable
membrane
Pump
Figure 21.19