Pleasant Day to the Practitioners of the CS art, Sweat, its helpful, sometimes distracting, its always with us. Lets examine it in more detail and see what is really going on. Its more than just water on the skin. It involves the skin, glands, hormones, electrical stimuli, and homeostasis. It can indicate a normal healthy body or one which is very sick. The secretion of sweat serves, through evaporation, to cool the body. When "no visible" perspiration is produced, the sweat glands release virtually pure water. This thin invisible coating of water maintains the skin moisture and is called "insensible perspiration". The glands of the skin must always be producing water to keep the skin moist. This insensible perspiration may amount to 600 to 700 ml / day. The small amount of organic and inorganic material that accumulates on the skin under these conditions is probably associated with activity of sebaceous glands rather than with that of the sweat glands. In circumstances in which visible sweat (sensible sweat) is elaborated, its volume and composition vary and are determined by the rate of evaporation, previous fluid intake, external temperature and humidity, and hormonal factors. Volumes as large as 14 liter per day have been recorded. Both volume and salt content of sensible perspiration are influenced by acclimation of the individual. Persons new to an environment that is hot and humid produce copious quantities of salt laden perspiration, Na+ (sodium) and Cl- (chloride) may be as high as 75 meq / l. Acclimated individuals, however, produce smaller volumes with a lower salt concentration. Unreplaced loss of large volumes of perspiration may result in hypertonic contraction. Miners' or stokers' cramps result from salt loss under these circumstances and can be prevented by incorporation of small amounts of salt in drinking water. In cystic fibrosis, a congenital defect involving most or all of the glandular epithelial structures of the body, sweat and tears are characteristically rich in salt. When small volumes of visible perspiration are elaborated, its concentration of nonprotein nitrogenous materials slightly exceed that of the plasma from which it is derived. This probably reflects evaporation of water from the elaborated sweat. However, sweat glands may possess an active mechanism for the concentration of lactic acid. The lactate concentration of the sweat of athletes far exceeds that present in plasma . Specific gravities of 1.002 to 1.005 for sweat have been reported, and the pH lies between 4.5 and 7.5. Approximate concentration of electrolytes in sweat:
Na+ <85, K+ 3-6 , Ca ++ 3-5, Cl- <85, HCO--- 0-10, Protein trace Numbers are meq / l of water. Lets look at secretion at the glandular level. Sweat is a secretion of glands in the skin. Formation of interstitial fluid from plasma may be described in physiochemical terms based on knowledge of the diffusibility of water, the solutes of plasma, and the permeability of the capillary wall to these substances. The basis for the differences between the composition of intracellular and extracellular fluid is the existence of a mechanism whereby energy, derived from metabolic processes, may be used to maintain the intracellular composition against an osmotic gradient. Another situation, "secretion", is evident in which cells are aligned in columnar fashion (tubes), bathed by interstitial fluid or plasma on one side and fluid of different composition on the opposite side, and in which differences in the composition of the two fluids cannot be accounted for in terms of spontaneous diffusion, osmosis, or permeability. The secretory process, operating against an osmotic, electrochemical, or hydrostatic gradient, again requires the harnessing of metabolically derived energy. This energy is derived from the mitochondria in the cuboidal and columnar cells which are secreting. The secretory process is characterized by (1) inhibition by interruption of cellular metabolism, (2) cations and anions are transported simultaneously in equivalent amounts in the same direction, in contrast to the Donnan equilibrium, (3) nonelectrolites also participate, and (4) cells are so aligned that the transported fluid leaves by a duct and the pressure within this duct is independent of arterial pressure. Mammalian secretions include milk, sweat, tears, cerebrospinal fluid, aqueous humor, and the fluids of the digestive tract. Among the more dramatic instances of secretion are the elaboration of 0.16 N HCL by the stomach, secretion of almost pure water by sweat glands, and removal of almost all glucose and Na+ from the urine. The fundamental mechanisms may be , in each case, an adaptation of those by means of which all cells maintain their internal composition. The mechanisms involved in these active transfers have been extensively studied but remain among the major unresolved areas of biochemistry. The term "secretion" has also been generally employed to describe the behavior of the ductless endocrine glands, although the cells "do work" in synthesizing the material, the actual transfer of the secretion operates with the osmotic gradient and no work need be done to achieve the transfer. --to be continued-- Bless you, Bob Lee -- oozing on the muggy shore of the gulf coast l...@fbtc.net -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: silver-list-requ...@eskimo.com -or- silver-digest-requ...@eskimo.com with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: silver-list@eskimo.com Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <mdev...@eskimo.com>
