(2) Sometimes, the skin color varies for reasons other than genetic.
(3) Not only is the color of the integument determined by genes, the pattern
of distribution of the color is determined by other genes.
Section III. INTEGUMENTARY DERIVATIVES
A number of structures are derived from the layers of the integument proper.
These structures are referred to as the integumentary derivatives or "appendages."
More or less covering the body are derivatives called hairs. The hairs of the
body vary in construction from area to area. An individual's genes determine the
specific construction, growth, and pattern of hairs for that individual. Sex hormones
more or less control the distribution of hairs (sexual dimorphism). Also, in different
cultures of human beings, different patterns of hair growth have arisen because of
Another integumentary derivative is the nails. A nail covers the dorsal aspect of
the end of each digit (fingers and toes).
The various glands are another kind of integumentary derivative.
a. Sweat Glands. There are at least two types of sweat (sudoriferous) glands:
(1) The general type throughout the body. This type produces a sensible
(2) A second type found in special areas. This type is found especially in the
palms of the hands. Such sweat glands respond to emotional stresses to produce the
"clammy" hands of the frightened individual.
b. Sebaceous Glands. Oil-producing (sebaceous) glands are usually found in
relationship to the hair follicles. The oily product of these glands keeps the following
(1) The outer layers of the skin.