Sweat Glands

Sweat glands occur nearly all over the skin. They are only absent in the red of the lips and the glans penis. They occur in particularly large numbers on the forehead, the palms of the hands and the soles of the feet (400 per cm²). Altogether, the body has about 2 million sweat glands. The end section (diameter: 4 mm) is curled up and is located at the junction between the dermis and subcutis. The excretory duct then extends to the surface, the end part winding through the epidermis.ABB.10 Sweat is a filtrate of blood and contains only little protein. It consists of 99 % water, is very runny, and is acidic (pH 4 – 6.8). In terms of ions, it contains above all sodium chloride, but also potassium and magnesium chloride, urea, amino acids, ammonia, uric acid, vitamins and traces of medication. Foodstuffs (e.g. garlic) are also sometimes excreted in the sweat.

Sweat glands play an important role in temperature regulation by causing cooling through evaporation of moisture on the surface of the skin. The skin is warmed by the capillary vessels in the finger-like ridges of the dermis under the epidermis (papillae of the dermis). The sweat glands are controlled by (cholinergic, sympathetic) nerves. Even when we do not sweat visibly, fluid is constantly evaporating from the surface of the skin (approx. 500 ml per day). In rooms with dry, heated air and in air-conditioned surroundings (e.g. aircraft), relatively high volumes of fluid are released unnoticed. At higher temperatures, sweating begins in the face and then spreads over the whole body to the palms of the hands and soles of the feet. Nervous (stress-related) sweat secretion (approx. 70 – 700 ml per hour) begins at the hands and feet. Maximum sweat secretion can be about 1 litre per hour or up to 18 litres per day