Eccrine Sweat Secretion

The eccrine sweat glands are one of two parts of the body's exocrine gland system, the system that regulates the release of fluids through the skin. The eccrine glands release sweat (perspiration), a fluid comprising water and various minerals, chiefly sodium. An eccrine gland does not lose any cellular material through the secretion process. The eccrine sweat glands are located throughout the skin surface, with the exception of the lips and the sexual organs; the greatest concentration of these glands is in the axilla (armpits), palms of the hands, and soles of the feet. The second type of exocrine glands are the apocrine glands, which chiefly produce and secrete scents unique to each person and are associated with the body's sex hormones. These glands secrete small amounts of sweat, and are located primarily in the vicinity of the armpit and genital regions, opening through the hair follicles.

Both the eccrine glands and the apocrine glands are located in the dermis, the underlayer of the skin, with a duct leading through the epidermis to the surface. The average adult person has approximately 2.5 million excretory ducts leading to the surface of the skin. Because the chief function of the eccrine gland is secreting sweat, these glands play an important role in thermoregulation. The sweat released by way of the eccrine glands is an important way to cool the body, especially during warm weather exercise, as the sweat excreted from the eccrine glands evaporates on the skin surface.

The most common form of malfunction in the eccrine glands is a blockage of the ducts leading to the skin surface. When the duct is blocked or ruptured in the dermis, a condition known as miliaria rubra (prickly heat) may result, causing a painful reddish inflammation of the skin. The condition is most common in infants and obese people, as well as others exposed to heat for extended periods.

The rate at which any person produces eccrine sweat is determined by factors such as genetic makeup, the level of individual physical conditioning, and the acclimatization that the person has developed with respect to heat. The rate and composition of eccrine sweat is often analyzed by sports scientists to assess how often and with what type of fluid replacement product an athlete should hydrate. Elevated concentrations of sodium in sweat will usually require an athlete to employ a hydration strategy that includes greater levels of sodium replacement, such as that available in salt tablets or sports drinks. In warm weather exercise, if an athlete is observed to be producing little or no eccrine sweat, such a circumstance is consistent with the onset of hyperthermia, which if untreated often leads to the serious and potentially fatal condition of heat stroke.

Excessive sweat can also be induced through psychological effects. When an athlete is affected by the nervous pressures of competition, as an example, the eccrine glands located in the palms of the hands and the soles of the feet will be stimulated by the sympathetic nervous system to produce greater amounts of sweat.

see also Acclimatization; Thermoregulatory system; Warm weather exercise.