Changes: Sweating

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Sweating (also called perspiration or sometimes transpiration) is the loss of sweat a watery fluid, consisting mainly of sodium chloride and urea in solution, that is secreted by the sweat glands in the skin of mammals. Sweat also consist of the chemicals or odorants 2-methylphenol and 4-methylphenol.

In humans, sweating is primarily a means of temperature regulation. Evaporation of sweat from the skin surface has a cooling effect due to the latent heat of evaporation of water. Hence, in hot weather, or when the individual's muscles heat up due to exertion, more sweat is produced. Sweating is increased by nervousness and nausea and decreased by cold. Animals with few sweat glands, such as dogs, accomplish similar temperature regulation results by panting, which evaporates water from the moist lining of the oral cavity and pharynx.

Sweat glands

In humans, there are two kinds of sweat glands which differ greatly in both the composition of the sweat and its purpose[1] :

Eccrine

Eccrine sweat glands, which are distributed over the entire body surface. These produce sweat that is composed chiefly of water with various salts. These glands are used for body temperature regulation.

Eccrine sweat glands are coiled tubular glands derived from the outer layer of skin but extending into the inner layer. They are distributed over almost the entire surface of the body in humans and many other species, but are lacking in some marine and fur-bearing species. The sweat glands are controlled by sympathetic cholinergic nerves which are controlled by a centre in the hypothalamus. The hypothalamus senses core temperature directly, and also has input from temperature receptors in the skin and modifies the sweat output, along with other thermoregulatory processes.

Human eccrine sweat is composed chiefly of water with various salts and organic compounds in solution. It contains minute amounts of fatty materials, urea, and other wastes. The concentration of sodium varies from 35–65 mmol/l and is lower in people acclimatised to a hot environment. The sweat of other species generally differ in composition.

Apocrine

For other uses of the word apocrine, see: apocrine gland

Apocrine sweat glands produce sweat that contains fatty materials. These glands are mainly present in the armpits and around the genital area and their activity is the main cause of sweat odour, due to the bacteria that break down the organic compounds in the sweat from these glands. Emotional stress increases the production of sweat from the apocrine glands, or more precisely: the sweat already present in the tubule is squeezed out. Apocrine sweat glands essentially serve as scent glands. East Asian people typically have markedly fewer of these glands compared to people of other ethnicities [2], which is why East Asian people generally do not emit such odors.

In some areas of the body, these sweat glands are modified to produce wholly different secretions, however, including the cerumen ("wax") of the outer ear. Others are greatly enlarged and modified to produce milk.

The neuroanatomy of sweating

The peripheral nerve link with sweat glands is through sympathetic Group C fibers releasing acetylcholine which binds to the Muscarinic acetylcholine receptor M3 to begin sweat production.

Emotional sweating arises from signals emanating from the amygdala, prefrontal cortex, insula and cingulum, which follow the same routes as for hypothalamic autonomic sweat innervation. This causes vasoconstriction of blood vessels in the skin giving the characteristic cold sweat of emotion

This is diferent from temperature-related sweating, where raised temperature leads to vasodilation warmer sweating .

References

Ferner S, Koszmagk R, Lehmann A, Heilmann W., Z Erkr Atmungsorgane. 1990;175(2):70-5. 'Reference values of Na(+) and Cl(-) concentrations in adult sweat'

External link

http://www.allaboutsweat.com
Detailed information concerning Hyperhidrosis
Sweating treatments, Causes and Information
For women, nothing's like the smell of men's sweat -- from Reuters (February 2007)
Male sweat boosts women's hormone levels -- from UC Berkeley, February 2007
The Effect of Male Sweat on Women's Hormone Levels -- from Science Daily, February 2007

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@@ Line 21: / Line 21: @@
 In some areas of the body, these sweat glands are modified to produce wholly different secretions, however, including the [[cerumen]] ("wax") of the outer [[ear]]. Others are greatly enlarged and modified to produce [[milk]].
+==The neuroanatomy of sweating==
+The [[peripheral nerve]] link with [[sweat glands]] is through sympathetic [[Group C fibers]] releasing [[acetylcholine]] which binds to the [[Muscarinic acetylcholine receptor M3]] to begin [[sweat]] production.
+'''Emotional sweating''' arises from signals emanating from the [[amygdala]], [[prefrontal cortex]], [[insula]] and [[cingulum]], which follow the same routes as for hypothalamic autonomic sweat innervation. This causes [[vasoconstriction]] of blood vessels in the [[skin]] giving the characteristic cold sweat of emotion
+This is diferent from '''temperature-related sweating''', where raised temperature leads to vasodilation  warmer sweating .
 ==See also==