Section IV. SKIN
2-10. DESCRIPTION OF SKIN
The skin is a tough, elastic structure covering the entire body (Figure 2-9). It is
made up of two principal layers, the epidermis or cuticle and the dermis or true skin.
The epidermis, which overlies the dermis, is itself composed of a superficial layer and
an inner layer. The superficial or horny layer consists of dead cells that are constantly
being worn off. These are replaced from the living cells that form the inner layer. The
dermis is the thicker part of the skin, and consists of connective tissue containing blood
vessels, nerve endings, sweat glands, sebaceous glands, and hair follicles. The dermis
is held in place by a layer of areolar connective tissue.
Figure 2-9. Structure of the skin (cross section).
2-11. FUNCTIONS OF THE SKIN
a. Protection. The skin protects underlying structures by acting as a
mechanical barrier. When the skin is broken, bacteria may invade the body through the
opening.
b. Regulation of Body Temperature. The skin regulates the body temperature
by controlling heat loss in two ways:
(1) The blood vessels in the skin change in size; they dilate and bring warm
blood to the surface to increase heat loss, and they constrict to decrease heat loss.
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