Protection.The skin performs many useful and necessary functions. Among these, that of protection stands out conspicuously. The skin, because of its peculiar location, is subjected to many forms of injury and irritation of a mechanical or chemical nature. These must be resisted or minimized, to safeguard the delicate and deeper vital structures. This protection is accomplished chiefly by the horny cells of the epidermis, the pigment, and the fat deposits. To illustrate, the protection against sunlight will serve as an admirable example. The sun’s rays, beating down upon a sensitive skin, irritate its surface. The pigment, or coloring matter of the skin, screens out the harmful rays, preventing their penetration into the deeper parts. If the normal amount of coloring matter is insufficient, Nature supplies additional pigment. This excess of pigment, known as freckling, is Nature’s effort to preserve the vital organs against excessive light irritation. Against injury, either of a physical or chemical nature, the hard, tough, horny cells constitute a most efficient barrier, and against violent blows or falls, excel-lent protection is afforded by the rather rich fat deposits throughout the depths of the skin.
Absorption.Another property of the skin is that of absorption. This is well shown in the dryness of the skin surface following massage with an ointment or cream. While these fatty sub-stances are apparently absorbed by the skin, water or watery solution cannot penetrate its depths. The nonabsorption of water by the skin is due to the presence of oil particles in the horny cells of the epidermis and, therefore, bathing, swimming and other aquatic maneuvers are made possible by ingenious Nature.
Yet, in spite of the many safeguards, the skin is vulnerable at times, for germs may gain entrance to the different portions of the skin through the sweat glands and hair sacs.
Excretion and Secretion.The skin also serves as an organ of excretion and secretion. It secretes sweat. It excretes various poisonous sub-stances from the body, but only to a minor degree, as the intestines and kidneys perform this function to the greatest extent. In certain serious diseases of the kidneys, an unusual burden is thrown upon the skin, often causing the emission of a peculiar, urine-like odor from its surface.
Temperature Regulation.In the regulation of body temperature, the skin plays a most important role. In health, the temperature of blood is maintained at a nearly constant point, although the body temperature may be subjected to wide variations. When the body is overheated, the blood is sent from the interior of the body to the blood vessels of the skin, where the heat is reduced to normal through radiation, conduction and increased sweating. When the individual is exposed to cold, contraction of the vessels and diminution or cessation of sweat occur, and the loss of heat is prevented.
Sensations.The different sensations of the skin, such as heat, cold, pain, etc., are made perceptible by the various nerves and nerve endings located within its boundaries.
Respiration or Breathing.The skin is also an organ of breathing (respiration). In this regard, its activity is slight, as compared to that of the lungs.