Sweat glands are located all over the body in the skin. In some places they are relatively common. Thus one finds about 300 sweat glands in 1 cm² of the skin of the palm, and on the back only 50. They are located in the lower layer of the dermis.
The ducts of the sweat glands open out on the surface of the cuticle (epidermis). At the basis of the sweat glands lie, in a circle, muscle cells between the gland cells. Because of the contraction of the muscles the gland secretion, sweat, is pressed out. Sweat glands have a special form of secretion. They deliver a portion of the cell as secretion. As a result, the cell becomes smaller. After a subsequent growth phase secretion is again possible.
At a normal temperature the body separates 300 to 500 ml of sweat per day. At high temperatures and physical exertion it is a multiple thereof. Perspiration is controlled by the autonomic nervous system and hormones. Increased sweating is not only a result of temperature fluctuations, but also from nervousness and hormonal changes, for example in women in transition. The sweat secretion plays an important role in the heat balance of the organism.
For the evaporation of water heat energy is needed. Evaporation of sweat consumes this energy, leading to cooling of the body. The main objective of this process is to keep up the normal body temperature, i.e., about 37 °C.