sebaceous gland

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sebaceous gland

(səbā`shəs), gland in the skinskin,
the flexible tissue (integument) enclosing the body of vertebrate animals. In humans and other mammals, the skin operates a complex organ of numerous structures (sometimes called the integumentary system) serving vital protective and metabolic functions.
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 of mammals that secretes an oily substance called sebum. In humans, sebaceous glands are primarily found in association with hairhair,
slender threadlike outgrowth from the skin of mammals. In some animals hair grows in dense profusion and is called fur or wool. Although all mammals show some indication of hair formation, dense hair is more common among species located in colder climates and has the
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 follicles but also occur in hairless areas of the skin, except for the palms of the hand and soles of the feet. Sebum is a mixture of fat and the debris of dead fat-producing cells. These cells are constantly replaced by new growth at the base of the glands. Generally the sebum is deposited on the hairs inside the follicles and is brought up to the surface of the skin along the hair shaft. In hairless areas, the sebum surfaces through ducts. Sebum lubricates and protects the hair and skin and prevents drying and irritation of membranes. Sebum may collect excessively as a result of poor hygiene, a diet rich in fats, or accelerated glandular activity, especially during adolescence. Excessive secretions of sebum may be related to acneacne,
common inflammatory disease of the hair follicles and sebaceous glands characterized by blackheads, whiteheads, pustules, nodules and, in the more severe forms, by cysts and scarring. The lesions appear on the face, neck, back, chest, and arms.
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, certain forms of baldnessbaldness,
thinning or loss of hair as a result of illness, functional disorder, or hereditary disposition; also known as alopecia. Male pattern baldness, a genetic trait, is the most common cause of baldness among white males.
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, and other skin disorders.

Sebaceous Gland


in humans and other mammals, a simple acinous gland with a short excretory duct and a branched end section that is located in the skin between the papillary and reticular layers of the dermis and that secretes cutaneus sebum. Sebaceous glands are distributed over the entire skin, except over the palmar and plantar surfaces.

Generally, sebaceous glands are connected to hairs: the excretory duct opens into the narrow fissure between the root and epithelial sheath of a hair. However, some glands, for example those on the lips, labia minora pudendi, nipples and nipple areas, and head and foreskin of the penis, open directly onto the body surface. The excretory duct is lined with stratified squamous epithelium, which on one side directly becomes the malpighian layer of the hair’s external root sheath and on the other becomes the wall of the alveolus. The latter consists of cells that are only slightly differentiated and capable of mitosis. These cells are rich in RNA and various enzymes and are especially concentrated near the excretory duct. The alveolus is filled with cells that contain fat droplets. Deep in the alveolus, cells undergo fatty degeneration, and as a result, their fat content increases and their nucleus wrinkles and decomposes.

Cutaneus sebum is formed from the remains of destroyed cells and fat. It serves as a fatty lubricant for the hair and skin surface and makes the skin elastic and impermeable to water, chemical substances, and certain microorganisms. The secretion of cutaneous sebum is promoted by the contraction of the skin musculature. The musk glands of certain reptiles and mammals and the uropygial glands of birds are sebaceous glands. In humans, the most common diseases of the sebaceous glands are atheroma, acne, and seborrhea.


sebaceous gland

[si′bā·shəs ′gland]
A gland, arising in association with a hair follicle, which produces and liberates sebum.
References in periodicals archive ?
The cells of the pilosebaceous unit which metabolize androgen including follicular keratinocytes and sebocytes and the androgenic effects on them are inhibited and a decrease of 12.5-65% occurs in sebum secretion.
It is the most common dermatologic disorder affecting approximately 85% of the teenagers [2, 3] and a chronic inflammatory follicular disorder of the skin, occurring in specialized pilosebaceous units on the face consisting of the follicular canal with its rudimentary hair, and the group of sebaceous glands that surround and open on to the follicle [4-6].
As this bacteria thrives, it causes the pilosebaceous unit to bulge and then eventually rupture, causing varying degrees of inflammation in the surrounding skin.
Increased bacterial activity within the pilosebaceous unit is known to be one of the four key contributing factors in acne pathogenesis.
(32) To enter the pilosebaceous unit, these particles must have a volume-average diameter of less than 10 micrometers and they must have a BET surface area in the range of 2.5 square meters per gram to 1000 square meters per gram.
Hormones likely influence the development of the cysts from the pilosebaceous unit. If there is a single steatocystoma, it is called steatocystoma simplex.
Acne vulgaris is a chronic inflammatory disease of the pilosebaceous unit characterised clinically by non-inflammatory lesions, open and closed comedones and papules or pustules and nodules of varying degree of inflammation and depth distributed predominantly over face, back and chest.
It is an inflammatory disease of pilosebaceous unit, and the four major pathophysiological mechanisms are increased sebum production, follicular hyperkeratinization, proliferation of Propionibacterium acnes, and inflammation.
Acne vulgaris is a common dermatological condition characterized by hormonally-mediated sebum overproduction, follicular hyperkeratinization, and chronic inflammation of the pilosebaceous unit. Microbes, genetic susceptibilities, and various environmental factors have been linked to the pathogenesis of the condition.
Label-retaining cells reside in the bulge area of pilosebaceous unit: implications for follicular stem cells, hair cycle, and skin carcinogenesis.
Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous unit that is associated with significant psychosocial repercussions.1 The main targets for acne treatment modalities are follicular hypercornification, seborrhea induced by hyperandrogenism, inflammation and bacterial colonization of hair follicles by Propionibacterium acnes.2 It is characterized by variety of lesions ranging from comedones, papules, pustules, cysts, nodules which ultimately lead to scarring in most of the patients.
These include vasculature, climatic exposures (temperature), dermal matrix degeneration, chemicals and ingested agents (foods, alcohol, medications), pilosebaceous unit abnormalities, microbial organisms, ferritin expression, reactive oxygen species, increased neoangiogenesis, and dysfunction of antimicrobial peptides.