Formation of
SWEAT OCCURNS IN?
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Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammals. Two types of sweat glands can be found in humans: eccrine glands and apocrine glands.
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21 Nov 2011
Sweating (perspiration)
Anatomy Fitness Skincare and Beauty
Introduction to sweating
What is sweat?
Anatomy of sweat glands
Eccrine sweat glands
Apocrine sweat glands
Apoeccrine sweat glands
Innervation of the sweat glands
Eccrine sweat glands
Apocrine sweat glands
Thermoregulatory sweating (body temperature control)
Eccrine sweat glands
Apocrine sweat glands
Non-thermoregulatory sweating
Eccrine sweat glands
Apoeccrine sweat glands
Introduction to sweating
Sweat is a clear, odourless solution secreted by sweat glands, which are also known as sudoriferous glands. It is hypotonic, meaning that it has a lower concentration of electrolytes than the cells of the sweat glands. The body has millions of sweat glands which lie within the deep layers of the skin and connect via ducts to the epidermis (outer layer of skin) before opening out onto the skin surface.
Skin For more information, see Anatomy of the Skin.
Sweating is the primary mechanism by which the human body regulates its temperature. It occurs during waking and sleeping. Sweat glands secrete sweat in response to nervous stimuli, primarily heat stimuli, but also emotional and gustatory (food) stimuli.
What is sweat?
Sweat consists primarily of water and electrolytes. The primary electrolytes contained in sweat are sodium and chloride. Potassium, urea, lactate, amino acids, bicarbonate and calcium are also found. Approximately 1% of the total volume of sweat consists of proteins, including immunoglobulins (proteins that function as antibodies) and glycoproteins (proteins joined to carbohydrates which perform a range of functions in the body). It is acidic, with a pH of 4–6.
Anatomy of sweat glands
Sweat pictureSome 4 million sweat glands are distributed throughout the human dermis (skin). They can be classified as one of two distinct types, which are anatomically different in terms of size and structure and the nervous stimuli to which they respond, and which serve different functions in the sweating process:
Eccrine sweat glands: Constitute some 75% of all the body’s sweat glands (~3 million);
Apocrine sweat glands: Comprise the other 25% (~1 million);
Apoeccrine sweat glands: Mixed-type sweat glands known as apoeccrine glands are also found in humans.
Eccrine sweat glands
Eccrine sweat glands are tubular structures with long branches. They consist of:
A tightly coiled tubular portion responsible for secreting sweat, located deep within the skin layers. The tubular portion is 60–80 µm in diameter and 2–5 mm in length; and
A straight duct portion that transports the sweat to the skin surface. The duct portion fuses with the papillary layer of the dermis (the layer underlying the skin surface) and opens onto the skin surface. The duct portion is also 2–5 mm in length, but is slightly narrower in diameter compared to the tubular portion.
The eccrine glands consist of three cell types:
Dark cells: Cover most of the surface of the cavities in the secretory or tubular portion of the eccrine sweat gland;
Clear cells: Rest directly on the basement membrane (a thin, fibrous layer separating the inner and outer layers of skin) or on myoepithelial cells; and
Myoepithelial cells: Spindle-shaped cells which lie between the secretory cells of the sweat glands and the basement membrane, close to the junction between the tubular and secretory portion of the eccrine sweat gland. These cells are also found in apocrine glands.
Eccrine sweat glands develop in utero (during foetal development) and are distributed over the entire body, with the exception of the lip margins, nail beds, nipples, the inner surface of the prepuce (foreskin), labia minora (outer folds of skin of the vulva/vagina), glans penis (head of the penis) and glans clitoris. The distribution of eccrine sweat glands at other body sites is uneven. Sites at which eccrine glands are heavily concentrated include:
Soles of the feet: 620 ± 20 per cm2;
Palms of the hands: 300 ± 80 per cm2;
Armpits: 360 ± 60 per cm2;
Forehead: 360 ± 60 per cm2; and
Cheeks: 300 ± 80 per cm2.
Sites which have a low concentration of eccrine glands include:
Trunk: 65 ± 20 per cm2; and
Extremities (arms and legs): 120 ± 30 per cm2.
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