perspiration

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sweat

sweat or perspiration, fluid secreted by the sweat glands of mammalian skin and containing water, salts, and waste products of body metabolism such as urea. The dissolved solid content of sweat is only one eighth that of an equal volume of urine, the body's main vehicle of salt excretion; however, excessive sweating may produce severe salt loss (see heat exhaustion). Human sweat glands are of two types, eccrine and apocrine. The eccrine glands, found everywhere on the body surface, are vital to the regulation of body temperature. Evaporation of the sweat secreted by the eccrines cools the body, dissipating the heat generated by metabolic processes. The release of such sweat is usually imperceptible; yet even in cool weather an individual will lose from 1 pt to 3 qt of fluid per day. Only when environmental conditions are especially hot or humid, or during periods of exercise or emotional stress, does the output of sweat exceed the rate of evaporation, so that noticeable beads of moisture appear on the skin. When such conditions are extreme, the body may lose up to 20 qt of fluid per day. Production of sweat is controlled by the temperature-regulating center of the hypothalamus. The apocrine glands, which occur only in the armpits and about the ears, nipples, navel, and anogenital region, are scent glands. They function in response to stress or sexual stimulation, playing no part in temperature regulation. The apocrines exude a sticky fluid quite different from the watery sweat of the eccrines. Apocrine fluid is rich in organic substances that are odorless when fresh but are quickly degraded by bacteria on the skin to produce characteristic odors. Copious sweating in the armpits comes not from the apocrines but from the eccrines interspersed among them.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Perspiration

 

sweating, the formation of sweat and its excretion by the sweat glands onto the surface of the skin.

Perspiration is well manifested in man, higher and lower apes, and ungulates (mainly perissodactyls). In rodents, insectivores, bats, terrestrial predators, and lower mammals (duck-billed platypus and echidna) it is almost nonexistent. In man perspiration is continuous. It is performed principally by reflex action—reflex receptors are located in the skin, mucosa, and muscles. Adequate stimuli for the perspiration reflex are high air temperature, ingestion of hot or pungent food or large quantities of fluids, physical exertion, fever, and emotional states. Perspiration centers are located in the cerebral cortex, hypothalamus, medulla oblongta, and spinal cord. Perspiration may be increased or decreased by means of medicinal preparations. It depends on blood circulation in the skin: when the blood vessels are dilated it increases; when they are constricted it decreases. It is an adaptation of the body to temperatures over 33°C. Perspiration is involved in thermoregulation and in maintenance of the water and salt balances of the body. Perspiration is important as an excretory function, especially with diseases of the kidneys.

Perspiration disorders may be quantitative (general or local) or qualitative. Quantitative disorders are more frequent and are expressed as increase (hyperhidrosis), decrease (hypohidrosis), or absence (anhidrosis) of perspiration. General hyperhidrosis occurs with various infections, intoxications, functional disturbances of the endocrine glands (hyperthyroidism), and other diseases. Increased perspiration may also be produced by the severe emotional excitement of fear or pain, in which case on pale, cold skin a “cold sweat” appears. Local perspiration disorders arise with many skin diseases, such as eczema, psoriasis, and shingles. Hypohidroses and anhidroses are observed in the region of scars after burns and wounds, as well as in leprosy and certain vascular diseases. Disorders of perspiration arise most often when there is disease of various sections of the nervous system, such as expressed hyperhidrosis of the hands and feet, which occurs in neuroses.

Qualitative perspiration disorders are manifested by changes in composition and color of excreted sweat. Thus, the sweat may sometimes be fatty because of admixture with the secretions of the sebaceous glands in seborrhea. With diabetes mellitus it may contain increased sugar. With uremia, increased amounts of urea and uric acid are noted. Treatment is directed toward the basic disease. Local symptomatic agents are also used.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

perspiration

[‚pər·spə′rā·shən]
(physiology)
The secretion of sweat.
(chemistry)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

perspiration

1. the act or process of insensibly eliminating fluid through the pores of the skin, which evaporates immediately
2. the sensible elimination of fluid through the pores of the skin, which is visible as droplets on the skin
3. the salty fluid secreted through the pores of the skin; sweat
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005