The sebum also inhibits bacterial growth on the skin. The sebaceous glands are found all over the body, except on the palms of the hands and soles of the feet. They are small on the body trunk and limbs, but quite large on the face, neck and upper chest. The exact composition depends on heredity and diet. Sweating is regulated by the involuntary portion of the nervous system.
Sweat cools the body by evaporation, which removes heat from the body surface.
Apocrine glands are larger than eccrine glands. Apocrine secretion contains the same basic components as eccrine sweat, but it also contains fatty acids and proteins, giving the sweat a milky or yellowish color. The secretion is odorless, but bacteria on the skin decompose the fatty acids and proteins, giving it its characteristic musky odor. They are responsive to emotional stress. Ceruminous glands are modified sweat glands found in the lining of the external ear canal.