Sebaceous gland


Sebaceous gland

Infobox Anatomy
Name = Sebaceous gland
Latin = glandula sebacea
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GrayPage = 1069


Caption = Schematic view of a hair follicle with sebaceous gland.


Caption2 = Cross-section of all skin layers. A hair follicle with associated structures. (Sebaceous gland labeled at center left).
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MeshName = Sebaceous+glands
MeshNumber = A10.336.827
DorlandsPre = g_06
DorlandsSuf = 12392642
The sebaceous glands are glands found in the skin of mammals.

Locations and morphology

A branched type of acinar gland, these glands exist in humans throughout the skin except in the palms of the hands and soles of the feet.

Sebaceous glands can usually be found in hair-covered areas, where they are connected to hair follicles. The glands deposit sebum on the hairs, and bring it to the skin surface along the hair shaft. The structure consisting of hair, hair follicle, arrector pili muscle, and sebaceous gland is known as a pilosebaceous unit.

Sebaceous glands are also found in non-haired areas (glabrous skin) of eyelids, penis, labia minora, and nipples. Here, the sebum traverses ducts which terminate in sweat pores on the surface of the skin. Pores range in size from 50 to 80 μm on average [http://answers.google.com/answers/threadview?id=548539] .

The inner surface of the lip and the buccal surface of the cheek can potentially contain ectopic sebaceous glands commonly known as Fordyce's spots or Fordyce granules. These occur as yellowish circular dots that form clusters. Eighty percent of the population have Fordyce granules and these sebaceous glands are asymptomatic.

At the rim of the eyelids, meibomian glands are a specialized form of sebaceous gland. They secrete sebum into the tears coating the eye, to slow evaporation.

ebum

Sebaceous glands secrete a waxy substance called sebum (Latin, meaning "fat" or "tallow") that is made of fat (lipids) and the debris of dead fat-producing cells. In the glands, sebum is produced within specialized cells and is released as these cells burst; sebaceous glands are thus classified as holocrine glands.Sebum itself is odorless, but its bacterial breakdown can produce odors. Sebum is one cause of some people experiencing "oily" hair or skin if not washed for some time. Earwax is partly composed of sebum.

Sebum acts to protect and waterproof hair and skin, and keep them from becoming dry, brittle, and cracked.Fact|date=September 2008 It can also inhibit the growth of microorganisms on skin.Fact|date=September 2008

Composition

The composition of sebum varies from species to species; in humans, the lipid content is as follows: [cite journal |author=Cheng JB, Russell DW |title=Mammalian wax biosynthesis. II. Expression cloning of wax synthase cDNAs encoding a member of the acyltransferase enzyme family |journal=J. Biol. Chem. |volume=279 |issue=36 |pages=37798–807 |year=2004 |pmid=15220349 |doi=10.1074/jbc.M406226200 |url=http://www4.utsouthwestern.edu/moleculargenetics/pdf/dr_cur_res/JBiolChem2004-II.pdf]

Changes during development

The sebaceous glands of a human fetus "in utero" secrete a substance called Vernix caseosa, a "waxy" or "cheesy" white substance coating the skin of newborns.

The activity of the sebaceous glands increases during puberty because of heightened levels of androgens. In males, sebaceous glands begin to appear predominantly on the penis during and after puberty. This is normal, however, and not to be confused with an STD.In females, they appear predominantly in the labia minora.

Pathology

Sebaceous glands are involved in skin problems such as acne and keratosis pilaris. The prescription drug isotretinoin significantly reduces the amount of sebum produced by the sebaceous glands, and is used to treat acne.

The extreme use (up to 10 times doctor prescribed amounts) of anabolic steroids by bodybuilders for muscle gain and repartitioning effects tend to stimulate the sebaceous glands which can cause acne. [ [http://www.steroid.com/sitenews/?EC=ReadArticle&ArticleID=5 Abuse Of Anabolic Steroids Causes Acne In Bodybuilders] , by Medinda.com]

A blocked sebaceous gland can result in a sebaceous cyst.

One condition involving enlarged sebaceous glands is known as sebaceous hyperplasia. Another common condition is seborrheic dermatitis.

Sebaceous gland carcinoma is a rare and aggressive form of cancer involving the sebaceous glands; sebaceous adenoma is a more benign neoplasm of the sebaceous glands.

Importance to other animals

Certain species of Demodex mites feed on sebum and are commonly found in the sebaceous glands of mammals, including those of humans.

The preputial glands of mice and rats are large modified sebaceous glands that produce pheromones.


=Additional

References

External links

* - "Integument: scalp"


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Look at other dictionaries:

  • sebaceous gland — any of the cutaneous glands that secrete oily matter for lubricating hair and skin. [1720 30] * * * Small oil producing gland in the skin, usually connected to a hair follicle by a duct into which it releases sebum, a component of the slightly… …   Universalium

  • sebaceous gland — UK / US noun [countable] Word forms sebaceous gland : singular sebaceous gland plural sebaceous glands medical an organ in your body that allows a type of oil called sebum to flow onto your skin and hair to keep them soft …   English dictionary

  • Sebaceous gland — A normal gland of the skin which empties an oily secretion into the hair follicle near the surface of the skin. * * * sebaceous gland n any of the small sacculated glands lodged in the substance of the derma, usu. opening into the hair follicles …   Medical dictionary

  • sebaceous gland — noun a cutaneous gland that secretes sebum (usually into a hair follicle) for lubricating hair and skin • Syn: ↑sebaceous follicle, ↑glandulae sebaceae • Hypernyms: ↑oil gland • Hyponyms: ↑Meibomian gland, ↑tarsal gland, ↑ …   Useful english dictionary

  • sebaceous gland — noun A gland of the skin which secretes an oily substance, sebum, usually into a hair follicle near the surface of the skin. Syn: sebaceous follicle, glandulae sebaceae …   Wiktionary

  • sebaceous gland — any of the simple or branched glands in the skin that secrete an oily substance, sebum. They open into hair follicles and their secretion is produced by the disintegration of their cells. Some parts of the skin have many sebaceous glands, others… …   The new mediacal dictionary

  • sebaceous gland — noun a small gland in the skin which secretes a lubricating oily matter (sebum) into the hair follicles to lubricate the skin and hair …   English new terms dictionary

  • sebaceous gland — seba′ceous gland n. anat. any of the cutaneous glands that secrete oily matter for lubricating hair and skin • Etymology: 1720–30 …   From formal English to slang

  • sebaceous gland — /səbeɪʃəs ˈglænd/ (say suhbayshuhs gland) noun any of the cutaneous glands which secrete oily matter for lubricating hair and skin …   Australian English dictionary

  • sebaceous gland —    Oil secreting glands, mostly clustered around hair follicles. The oil, sebum, is released into the oil glands from the disintegrated cytoplasm of shedding holocrine cells that line the alveolar surfaces. The nature of the secretion is often a… …   Herbal-medical glossary


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