77
CHAPTER THREE
Cells
7.5
µ
m
12
µ
m
140
µ
m
200
µ
m
(c)
(d)
(a)
(b)
(b)
Epithelial cells protect underlying cells.
(c)
Muscle cells contract, pulling structures
closer together.
(a)
A nerve cell transmits impulses from one body part to another.
FIGURE 3.2
Cells vary in shape
and function.
FIGURE 3.1
Cells vary
considerably in size. This illustration
shows the relative sizes of four types
of cells. (
a
) Red blood cell, 7.5 µm in
diameter; (
b
) white blood cell,
10–12 µm in diameter; (
c
) human
egg cell, 140 µm in diameter;
(
d
) smooth muscle cell, 20–500 µm
in length.
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