Eccrine sweat gland

Eccrine glands (/ˈɛkrən/, /ˈɛˌkraɪn/, or /ˈɛˌkrin/; from ekkrinein "secrete"; sometimes called merocrine glands) are the major sweat glands of the human body, found in virtually all skin, with the highest density in palms and soles, then on the head, but much less on the trunk and the extremities. In lower mammals, they are relatively sparse, being found mainly on hairless areas such as foot pads. They reach their peak of development in humans, where they may number 200-400/sq. cm of skin surface. They produce a clear, odorless substance, consisting primarily of water and NaCl. NaCl is reabsorbed in the duct to reduce salt loss, but is dysfunctional in cystic fibrosis thus producing salty sweat. They are active in thermoregulation by providing cooling from water evaporation of sweat secreted by the glands on the body surface and emotional induced sweating (anxiety, fear, stress, and pain). The white sediment in otherwise colorless eccrine secretions is caused by evaporation that increases the concentration of salts.