Sweat glands, also known as sudoriferous glands, are small tubular structures of skin that produce sweat. They are distributed all over the skin, except lips, glans penis and nail bed. These glands are of two types: Eccrine and Apocrine.
Eccrine sweat glands:
Eccrine glands are much more abundant and distributed in almost every part of the skin. Each one of these is a single tube, the deep part of which is coiled into a ball. The coiled part is called body of the gland. It lies in the deeper part of corium or in the subcutaneous tissue. The straight part is called duct. It traverses the dermis and epidermis and opens on the surface of the skin.
The glands are large in the axilla and groin. They are most abundant in the regions of palms and soles and least abundant in the neck and back.
The eccrine glands are merocrine in nature, which means that they produce their thin watery secretion without any disintegration of the epithelial cells. They are supplied and controlled by cholinergic sympathetic nerves.
The glands help in regulation of body temperature by evaporation of sweat and also help in excreting the body salts.
Apocrine sweat glands:
The apocrine are confined to axilla, eyelids (where they are known as Moll’s glands), nipple, and areola of the breast, perianal region and the external genitalia. They are larger than the eccrine glands and produce a thicker secretion having a characteristic smell. They develop in close association with hair and their ducts typically open into the distal ends of hair follicles.
The Ceruminous glands of the external auditory meatus are modified apocrine sweat glands. The apocrine glands also are merocirne in nature, but are regulated by a dual autonomic control. Some research workers are not inclined towards calling these glands as sweat glands. The main reason behind this is that they don’t respond sufficiently to temperature changes.
Average secretion of sweat:
On average, about one liter of sweat is secreted each day. The total water loss on daily basis for a healthy adult individual is about 1500 ml. This shows that greater part of the water lost from our body is in the form of sweat. In hot climates, the proportion rises to even a higher value and the secretion of sweat may amount to 3-7 liters per day. As long as the sweat glands are intact, the skin can regenerate, however, if the sweat glands are lost, skin grafting becomes necessary.