HUMAN BIOLOGY

tIssUes, orGans, and orGan systeMs 77

Figure 4.10 The body has eleven organ systems. Not shown is the immune system, which consists mainly of cells called lymphocytes.
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integumentary

System

Protects body from

injury, dehydration,

pathogens; moderates

temperature; excretes

some wastes; detects

external stimuli.

Nervous

System

Detects external

and internal stimuli;

coordinates responses

to stimuli; integrates

organ system

activities.

Endocrine System

Secretes hormones

that control activity

of other organ

systems. (Male

testes added.)

Reproductive

System

Female: Produces eggs;

nourishes and protects

developing offspring. Male:

Produces and transfers

sperm to a female.

urinary

System

Maintains volume

and composition

of blood; excretes

excess fluid and

wastes.

Lymphatic

System

Collects and returns

tissue fluid to the

blood; defends the

body against infection,

cancers.

Respiratory

System

Takes in the oxygen

for aerobic respiration;

expels carbon dioxide

released by this pathway.

Digestive

System

Takes in food and

water; breaks food

down and absorbs

needed nutrients,

then eliminates

food residues.

Muscular

System

Moves the body

and its parts;

maintains posture;

produces heat to

maintain body

temperature.

Circulatory

System

Distributes materials

and heat throughout

the body; helps

maintain pH.

Skeletal

System

Supports and protects

body parts; site of

muscle attachment;

produces red blood

cells; stores minerals.

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