The skin produces sweat which, when it evaporates, cools the body
c. Sensory Perception. The skin acts as an organ of perception. It contains
sensory nerve endings which are specialized to detect heat, cold) pressure (touch), and
d. Excretion. The excretion of waste products through the skin is a function of
the sweat glands that open by a duct onto the skin surface. The opening is called a
pore. These glands are distributed in large numbers over the body and secrete an
average of a quart of perspiration each day; although, the amount varies considerably,
depending on the temperature and humidity of the atmosphere, and the amount of
exercise performed by the individual. Perspiration is continuous, but it may be so slow
and the sweat may evaporate so quickly that it is imperceptible. Sweat consists chiefly
of water (99 percent), with small quantities of salts and organic materials which are
waste products. Skin also secretes a thick substance, sebum. This material is the
product of the sebaceous glands, and its purpose is to lubricate the skin and keep it soft
e. Absorption. Although not one of its normal functions, the skin is capable of
absorbing water and other substances. Physicians take advantage of this fact by
prescribing local application of certain drugs.
2-12. APPENDAGES OF THE SKIN
The appendages of the skin include the glands (sweat and sebaceous), the hair,
and the nails. Each hair consists of a shaft (the portion projecting from the surface) and
a root (the part implanted in the skin); each hair root is implanted in an involution of the
epidermis called the hair follicle. A fingernail or toenail grows from a nail bed. If the bed
is destroyed, the nail will no longer grow.
2-13. DISEASES OF THE SKIN
a. General. Diseases of the skin make up a large portion of the physician's
practice, whether in civilian life or in the Army. A specialist in diseases of the skin is
called a dermatologist. Descriptive terms used in dermatology are:
Bulla--large blister filled with serous fluid.
Excoriation--superficial discontinuity or scratch.
Lesion--any localized abnormality.
Macula--small, flat discoloration or freckle.