The nervous system and bodily hormones combine forces to regulate and control sweat glands, which are located virtually all over the body below the surface of the skin. Sweat glands have evolved as a primary method of cooling for humans. Increased physical activity causes a person’s body temperature to increase, and humans do not have a mechanism like panting to assist in cooling down. Instead, the body relies on sweat glands to secrete a clear, potentially odorous substance onto the surface of the skin in order to reduce the body temperature.
Sweat glands operate by secreting a substance comprised mostly of water, sodium chloride and electrolytes. Sweat, also called perspiration, is produced by the gland and then discharged onto the surface of the skin through a small tube leading to a pore. A pore is an opening on the surface of the skin, and the human body has thousands of pores through which sweat escapes.
Eccrine sweat glands are by far the most common in the human body, and exist in primates only. They are found nearly all over the body and have evolved in conjunction with the development of hairless skin in humans. These sweat glands are found in the highest concentrations on the scalp, the soles of the feet and the palms of the hands.
Apocrine sweat glands are located in the canals where hair follicles exist, so they are found in areas like the armpits and pubic region. They begin secreting around puberty, and the secretion can be cloudy instead of clear like normal sweat. These secretions are known to contain pheromones, which are chemicals that can alter hormonal balances in other people. The exact relationship between apocrine sweat glands and their affect on hormones in the body is not fully known.
There are other glands that are similar to sweat glands, but they secrete very different substances. Mammary glands are considered to be a type of sweat gland that produces milk. Ceruminous glands are located in the ear and produce ear wax.
Excessive sweating can lead to dehydration. With extreme exertion or heat, the body’s eccrine glands can secrete in excess of three liters of fluid per hour. Therefore, it is vital to replenish these fluids as soon as possible. In addition, electrolytes from the body’s plasma can be removed during vigorous sweating episodes. Anyone who is sweating profusely for extended periods must replenish the water and electrolytes, commonly through beverages supplemented with electrolytes.