Sweat Glands

About the Sweat Glands

Sweat glands are coiled tubular glands in the skin. Eccrine glands, the most numerous, are distributed over almost the entire body surface and are especially dense on the palms, soles, and forehead. They open directly onto the skin and secrete a watery fluid containing salt, whose evaporation cools the body, making them central to temperature regulation in humans, who have an unusually high capacity for sweating among mammals. They are controlled by sympathetic nerves that, unusually, use acetylcholine as their transmitter. Apocrine glands, found mainly in the armpits and groin, become active at puberty and release a thicker secretion into hair follicles; this is odorless when produced, but skin bacteria break it down into compounds responsible for body odor. Modified apocrine glands include the ceruminous glands that help produce earwax and the mammary glands. Excessive sweating is called hyperhidrosis, while reduced sweating can increase the risk of heat illness. In cystic fibrosis, sweat contains abnormally high salt levels, the basis of the sweat test.