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Chapter 3
F U N C T I O N A L A N AT O M Y O F C E L L S
The principle of complementarity of structure and function was
introduced in Chapter 1 and is evident in the relationships that
exist between cell size, shape, and function. Almost all human
cells are microscopic in size (Table 3-1). Their diameters range
from 7.5 micrometers (m) (red blood cells) to about 150 m
(female sex cell or ovum). The period at the end of this sentence
measures about 100 m—roughly 13 times as large as our small-
Table 3-1
Anatomy of Cells
est cells and two thirds the size of the human ovum. Like other
anatomical structures, cells exhibit a particular size or form because they are intended to perform a specialized activity. A nerve
cell, for example, may have threadlike extensions over a meter in
length! Such a cell is ideally suited to transmit nervous impulses
from one area of the body to another. Muscle cells are specialized
to contract or shorten. Other types of cells may serve protective or
secretory functions (Table 3-2).
Units of Size
UNIT
SYMBOL
EQUAL TO
USED TO MEASURE
Centimeter
cm
1/100 meter
Objects visible to the eye
Millimeter
mm
1/10 centimeter
Very large cells; groups of cells
Micrometer (micron)
m
1/1000 millimeter
Most cells; large organelles
Nanometer
nm
1/1000 micrometer
Small organelles; large biomolecules
Angstrom
1/10 nanometer
Molecules; atoms
Table 3-2
TYPE
Nerve cells
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A
Example of Cell Types
EXAMPLE
STRUCTURAL FEATURES
FUNCTIONS
Surface that is sensitive to stimuli
Detect changes in internal or external
environment
Transmit nerve impulses from one part of
the body to another
Long extensions
Muscle cells
Elongated, threadlike
Contain tiny fibers that slide together
forcefully
Contract (shorten) to allow movement of
body parts
Red blood cells
Contain hemoglobin, a red pigment that
attracts, then releases, oxygen
Transport oxygen in the bloodstream
(from lungs to other parts of the body)
Gland cells
Contain sacs that release a secretion to
the outside of the cell
Release substances such as hormones,
enzymes, mucus, and sweat
Immune cells
Some have outer membranes able to
engulf other cells
Some have systems that manufacture antibodies
Some are able to destroy other cells
Recognize and destroy “nonself ” cells
such as cancer cells and invading
bacteria