9.12 : Accessory Structures of the Skin: Sweat Glands

Sweat glands or sudoriferous glands are one of the important accessory structures of the skin. They are small, coiled tubular structures located in the dermis, the middle layer of the skin. Sweat glands are responsible for producing and secreting sweat, a watery fluid that helps regulate body temperature and excrete waste products.

Sweat glands are classified as merocrine glands; that is, the secretions are excreted by exocytosis through a duct without affecting the cells of the gland. There are two types of sweat glands, each secreting slightly different products.

An eccrine sweat gland is a type of gland that produces hypotonic sweat for thermoregulation. These glands are found all over the skin's surface but are especially abundant on the palms of the hand, the soles of the feet, and the forehead. They are coiled glands lying deep in the dermis, with the duct rising to a pore on the skin surface, where the sweat is released. This type of sweat, released by exocytosis, is hypotonic and composed mostly of water, with some salt, antibodies, traces of metabolic waste, and dermcidin, an antimicrobial peptide. Eccrine glands are a primary component of thermoregulation in humans.

An apocrine sweat gland is usually associated with hair follicles in densely hairy areas, such as armpits and genital regions. Apocrine sweat glands are larger than eccrine sweat glands and lie deeper in the dermis, sometimes even reaching the hypodermis, with the duct normally emptying into the hair follicle. In addition to water and salts, apocrine sweat includes organic compounds that make the sweat thicker and subject to bacterial decomposition and a subsequent smell. The release of this sweat is under both nervous and hormonal control and plays a role in the poorly understood human pheromone response. Most commercial antiperspirants use an aluminum-based compound as their primary active ingredient to stop sweat. When the antiperspirant enters the sweat gland duct, the aluminum-based compounds precipitate due to a change in pH and form a physical block in the duct, which prevents sweat from coming out of the pore.

In addition to their role in temperature regulation, sweat glands contribute to the excretion of metabolic waste products, such as urea and ammonia, from the body. However, sweating can disrupt the electrolyte balance.

Overall, sweat glands are essential in maintaining thermoregulation and excretion processes in the body. Their activity is crucial in keeping the body cool and maintaining internal homeostasis.

This text is adapted from Openstax, Anatomy and Physiology 2e, Section 5.2: Accessary structures of skin.