2 the process of the sweat glands of the skin secreting a salty fluid; "perspiration is a homeostatic process" [syn: sweating, diaphoresis, sudation, hidrosis]
- Rhymes: -eɪʃǝn
process of perspiring
Perspiration (also called sweating or sometimes transpiration) is the production and evaporation of a fluid, consisting primarily of water as well as a smaller amount of sodium chloride (the main constituent of "table salt"), that is excreted by the sweat glands in the skin of mammals. Sweat also contains the chemicals or odorants 2-methylphenol (o-cresol) and 4-methylphenol (p-cresol).
In humans, sweating is primarily a means of thermoregulation, although it has been proposed that components of male sweat can act as pheromonal cues . 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. Primates and horses have armpits that sweat similarly to those of humans.
MechanismSweating is controlled from a center in the preoptic & anterior regions of the hypothalamus where thermosensitive neurones are located. The heat regulatory function of the hypothalamus is also affected by inputs from temperature receptors in the skin. High skin temperature reduces the hypothalamic set point for sweating and increases the gain of the hypothalamic feedback system in response to variations in core temperature. Overall though, the sweating response to a rise in hypothalamic temperature (‘core temp’) is much larger than the response to the same increase in average skin temperature.
Sweat is not pure water; it always contains a small amount (0.2 - 1%) of solute . When a person moves from a cold climate to a hot climate, adaptive changes occur in their sweating mechanism. These are referred to as acclimatisation: the maximum rate of sweating increases and its solute composition decreases. The daily water loss in sweat is very variable: from 100 to 8,000 mls/day. The solute loss can be as much as 350 mmols/day (or 90 mmols/day acclimatised) of sodium under the most extreme conditions. In a cool climate & in the absence of exercise, sodium loss can be very low (less than 5 mmols/day). [Na+] in sweat is 30-65 mmol/l depending on degree of acclimatisation.
CompositionSweat contains mainly water. It also contains minerals, as well as lactate and urea. Mineral composition will vary with the individual, the acclimatisation to heat, exercise and sweating, the particular stress source (exercise, sauna, etc.), the duration of sweating, and the composition of minerals in the body. An indication of the minerals content is is: sodium 0.9 gram/liter, potassium 0.2 gram/liter, calcium 0.015 gram/liter, magnesium 0.0013 gram/liter. Also many other trace elements are excreted in sweat, again an indication of their concentration is (although measurements can vary fifteenfold): zinc (0.4 mg/l), copper (0.3 - 0.8 mg/l), iron (1 mg/l), chromium (0.1 mg/l), nickel (0.05 mg/l), lead (0.05 mg/l). . Probably many other less abundant trace minerals will leave the body through sweating with correspondingly lower concentrations. In humans sweat is hyposmotic relatively to the plasma .
- 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
- K. Sato et al., "Biology of sweat glands and their disorders", Journal of the American Academy of Dermatology, April 1989
- 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'
- E. R. Nadel, R. W. Bullard, and J. A. Stolwijk, "Importance of skin temperature in the regulation of sweating", Journal of Applied Physiology, Vol. 31, Issue 1, 80-87, July 1, 1971
perspiration in Arabic: تعرق
perspiration in Aymara: Jump'i
perspiration in Azerbaijani: Tər
perspiration in Danish: Sved
perspiration in German: Schwitzen
perspiration in Modern Greek (1453-): Ιδρώτας
perspiration in Spanish: Sudor
perspiration in Esperanto: Ŝvito
perspiration in French: Sueur
perspiration in Indonesian: Keringat
perspiration in Icelandic: Sviti
perspiration in Italian: Sudorazione
perspiration in Hebrew: זיעה
perspiration in Latin: Sudor
perspiration in Lithuanian: Prakaitavimas
perspiration in Dutch: Zweten
perspiration in Japanese: 汗
perspiration in Polish: Pot
perspiration in Portuguese: Suor
perspiration in Simple English: Sweat
perspiration in Finnish: Hiki
perspiration in Swedish: Svettning
perspiration in Tamil: வியர்வை
perspiration in Turkish: Ter
perspiration in Yiddish: שוויצן
perspiration in Chinese: 汗液