/perr"speuh ray"sheuhn/, n.1. a salty, watery fluid secreted by the sweat glands of the skin, esp. when very warm as a result of strenuous exertion; sweat.2. the act or process of perspiring.[1605-15, in sense "a breathing through"; 1620-30 for current senses; < NL perspiration- (s. of perspiratio) imperceptible sweating, lit., a breathing through. See PERSPIRE, -ATION]Syn. 1. PERSPIRATION, SWEAT refer primarily to moisture exuded by animals and people from the pores of the skin. PERSPIRATION is often regarded as the more polite word, and is often used overfastidiously by those who consider SWEAT coarse; but SWEAT is a strong word and in some cases obviously more appropriate: a light perspiration; the sweat of his brow. SWEAT is always used when referring to animals or objects: Sweat drips from a horse's flanks. It may also be used metaphorically of objects: Sweat forms on apples after they are gathered.
* * *Fluid given off by the skin as vapour by simple evaporation or as sweat actively secreted from sweat glands to evaporate and cool the body.When the body temperature rises, the sympathetic nervous system stimulates eccrine sweat glands to secrete water to the skin surface, where it cools the body by evaporation. Human eccrine sweat is essentially a dilute solution of sodium chloride with trace amounts of other plasma electrolytes. In extreme conditions, human beings may excrete several litres of such sweat in an hour.
* * *in most mammals, water given off by the intact skin, either as vapour by simple evaporation from the epidermis (insensible perspiration) or as sweat, a form of cooling in which liquid actively secreted from sweat glands (q.v.) evaporates from the body surface. Sweat glands, although found in the majority of mammals, constitute the primary means of heat dissipation only in certain hoofed animals (orders Artiodactyla and Perissodactyla) and in primates, including humans. Their secretion is largely water (usually about 99 percent), with small amounts of dissolved salts and amino acids.When the body temperature rises, the sympathetic nervous system stimulates the eccrine sweat glands to secrete water to the skin surface, where it cools the body by evaporation. Thus, eccrine sweat is an important mechanism for temperature control. In extreme conditions, human beings may excrete several litres of such sweat in an hour.Human eccrine sweat is essentially a dilute sodium chloride solution with trace amounts of other plasma electrolytes. In some cases a reddish pigment may also be present. In a person unused to heavy sweating, the loss of sodium chloride during a period of heavy labour or high temperatures may be great (see sodium deficiency), but the efficiency of the gland increases with use, and in acclimatized persons the salt loss is decreased.The apocrine sweat glands, associated with the presence of hair in human beings (as on the scalp, the armpit, and the genital region), continuously secrete a concentrated fatty sweat into the gland tube. Emotional stress stimulates contraction of the gland, expelling its contents. Skin bacteria break down the fats into unsaturated fatty acids that possess a pungent odour.
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