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.

E. S. KIRPICHNIKOVA

sebaceous gland

[si′bā·shəs ′gland]
(physiology)
A gland, arising in association with a hair follicle, which produces and liberates sebum.
References in periodicals archive ?
Sebaceous glands were also reduced in size after therapy, and remained smaller for the duration of the 20 weeks of follow-up.
While previous research shows the Smoothbeam laser effectively treats the root cause of acne -- overactive, oil-producing sebaceous glands -- this is the first study to identify the length of time patients can experience clearing, regardless of their skin type.
Skin lesions caused by seborrheic dermatitis are typically located in areas abundant with sebaceous glands including the scalp, face and upper trunk.
The Phase I clinical trial was designed to study the uptake of the photosensitizer in hair follicles, sebaceous glands and the epidermis after topical administration to the back of 10 patients with acne.
It's chiefly used to treat facial skin conditions where a generous supply of hair follicles and sebaceous glands allow the skin to regenerate quickly without scarring.
Non-ablative therapy works by targeting the overactive sebaceous glands that are responsible for acne.
With the laser, heat is generated in and around the sebaceous glands, the root cause of acne, which are located in the upper layers of the skin.
Unlike resurfacing lasers that remove the top layers of skin, CoolTouch's non-ablative technology reaches deep down to alter the sebaceous glands where acne lesions occur without affecting the skin surface.
The cause is not clear, although it may be linked to overactive sebaceous glands, which produce an oily substance, called sebum.
Acne develops on those areas of the skin where sebaceous glands are most numerous: the face, scalp, neck, chest, back, and upper arms and shoulders.
During adolescence, this oversensitivity results in sebaceous glands becoming blocked by dead skin cells, which causes blackheads.