Sweat glands in human body

Humans perspire over nearly every inch of skin, but anyone with sweaty palms or
smelly feet can attest to the fact that sweat glands are most numerous in the palms
and soles, with the forehead running a close third. There are two types of sweat, or
sudoriferous, glands: eccrine and apocrine. Both are coiled tubules embedded in the
dermis or subcutaneous layer composed of simple columnar cells.

Eccrine glands are distributed widely over the body — an average adult has roughly
3 million of them — and produce the watery, salty secretion you know as sweat. Each
gland’s duct passes through the epidermis to the skin’s surface, where it opens as a
sweat pore. The sympathetic division of the autonomic nervous system controls when

and how much perspiration is secreted depending on how hot the body becomes.
Sweat helps cool the skin’s surface by evaporating as fast as it forms. About 99 percent
of eccrine-type sweat is water, but the remaining 1 percent is a mixture of sodium chloride
and other salts, uric acid, urea, amino acids, ammonia, sugar, lactic acid, and
ascorbic acid.

Apocrine sweat glands are located primarily in armpits (known as the axillary region)
and the groin area. Usually associated with hair follicles, they produce a white, cloudy
secretion that contains organic matter. Although apocrine-type sweat contains the
same basic components as eccrine sweat and also is odorless when first secreted, bacteria
quickly begin to break down its additional fatty acids and proteins — explaining
the post-exercise underarm stench. In addition to exercise, sexual and other emotional
stimuli can cause contraction of cells around these glands, releasing sweat.