Difference between Apocrine and Eccrine sweat glands

Skin (Layers, Glands, Vessels)

Apocrine vs Eccrine sweat glands

The skin is the largest organ of the human body. It consists of various structures like the sweat glands, hair follicles, blood vessels, nerve endings and the three layers- epidermis, dermis and hypodermis. One might be surprised to see that so many structures are present, perfectly organized in the thin layer of visible skin.

There are two types of sweat glands present in the skin layer; one kind are the apocrine sweat glands which secrete fluid into the sac of hair follicle through which it eventually comes out on the skin. The other kind is the eccrine sweat gland which secretes sweat directly onto the surface of the skin. One may equate the secretion of the glands as follows- the apocrine glands secrete substances indirectly whereas the eccrine glands secrete directly through a duct. Eccrine glands are also called as merocrine glands. Generally, in humans, the apocrine glands are present in very few numbers and are located at few select parts of the body whereas the eccrine glands are present all over the body in large numbers. In infants, the apocrine glands are present all over the body but eventually they are replaced and restricted to very few parts as seen in adults.

Apocrine glands are found in the armpits, areola of breast, perineum (area between anus and genitals), in the ear and in the eyelids while the eccrine glands are present all over the body except the above mentioned parts. The secretory part of the apocrine glands is larger than the secretory portion of the eccrine glands. Hence, the apocrine glands look larger than the eccrine glands. Apocrine glands are located deep in the layers of the skin but eccrine glands are superficially placed such that their ducts reach the surface of the skin directly. A very distinguishing feature of apocrine glands is that they are inactive before puberty. The hormonal surge during puberty brings about a change in the size of the glands and starts the functioning of these glands. Apocrine sweat glands secrete a fluid containing pheromone-like compounds which attracts the opposite sex. This phenomenon occurs in all mammals, not just humans. Apocrine glands are driven by adrenaline and hence, they increase in size during times of stress, sexual stimulation, anxiety, pain and fright. In contrast, the eccrine glands are employed in temperature control and cooling off the body along with excretion of unwanted substances by way of sweat. They also help in protection of the skin. Whenever there is excess heat in the body, the eccrine glands secrete a clear fluid called sweat which cools the surface of the skin. Eccrine glands are driven by neural as well as hormonal mechanisms and thus, serve as agents for temperature regulation in the body. Eccrine sweat glands excrete excess water and electrolytes by this mechanism. Certain ingredients in sweat like antibodies and immunoglobulins cause prevention of the bacterial colonization on the surface of the skin and hence, serve as a protective mechanism.

Apocrine glands secrete a thick clear fluid whereas the eccrine glands secrete a clear thin watery sweat. This sweat released by the eccrine glands consists of more water and sodium chloride compound which imparts the salty taste to the sweat.

Summary: Apocrine glands are considered as modified glands that secrete wax in the ears, milk in the areola of breast and secretions of the ciliary glands in the eyelids. Eccrine glands are sweat glands of the body and are widely distributed all over the body. Apocrine glands secrete substances by emptying them into a hair follicle while eccrine glands discharge directly through a duct onto the skin surface.

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