Sebaceous gland

This is a good article. Click here for more information.
Source: Wikipedia, the free encyclopedia.
(Redirected from
Sebum
)
"Oil gland" redirects here. For the secretion of oil by preening of birds, see Uropygial gland.
Not to be confused with Sebaceous adenitis.

skin layers. A hair follicle with associated structures. (Sebaceous glands labeled at center left.)
Identifiers
MeSHD012627
TA98A16.0.00.030
A15.2.07.044
TA27082
FMA59160
Anatomical terminology]

A sebaceous gland or oil gland

benign, visible, sebaceous glands found usually on the lips, gums and inner cheeks, and genitals
.

Structure

Location

Sebaceous glands are found throughout all areas of the skin, except the

hair follicles and those that exist independently.[4]

Sebaceous glands are found in hair-covered areas, where they are connected to

hair shaft. The structure, consisting of hair, hair follicle, arrector pili muscles, and sebaceous gland, is an epidermal invagination known as a pilosebaceous unit.[4]

Sebaceous glands are also found in hairless areas (

Montgomery's glands.[5]

Development

Sebaceous glands are first visible from the 13th to the 16th week of

SHH all increase the likelihood of sebaceous gland presence.[5]

The sebaceous glands of a human

newborns.[7] After birth, activity of the glands decreases until there is almost no activity during ages two–six years, and then increases to a peak of activity during puberty, due to heightened levels of androgens.[6]

  • Base of pilosebaceous unit
    Base of pilosebaceous unit
  • Insertion of sebaceous glands into hair shaft
    Insertion of sebaceous glands into
    hair shaft
  • Sagittal section through the upper eyelid.
    upper eyelid
    .
  • A hair follicle with associated structures
    A hair follicle with associated structures
  • Scalp cross section showing hair follicle with sebaceous glands.
    Scalp cross section showing hair follicle with sebaceous glands.

Function

Relative to keratinocytes that make up the hair follicle, sebaceous glands are composed of huge cells with many large vesicles that contain the sebum.

CFTR (see Fig. 6 and Fig. 7 in reference[8]
).

Sebaceous glands secrete the oily, waxy substance called sebum (

wax esters, squalene, and metabolites of fat-producing cells. Sebum lubricates the skin and hair of mammals.[9] Sebaceous secretions in conjunction with apocrine glands also play an important thermoregulatory role. In hot conditions, the secretions emulsify the sweat produced by the eccrine sweat glands and this produces a sheet of sweat that is not readily lost in drops of sweat. This is of importance in delaying dehydration. In colder conditions, the nature of sebum becomes more lipid, and in coating the hair and skin, rain is effectively repelled.[10][11]

Sebum is produced in a

holocrine process, in which cells within the sebaceous gland rupture and disintegrate as they release the sebum and the cell remnants are secreted together with the sebum.[12][13] The cells are constantly replaced by mitosis at the base of the duct.[4]

Sebum

Sebum is secreted by the sebaceous gland in humans. It is primarily composed of

free fatty acids (≈16%).[7][14] The composition of sebum varies across species.[14] Wax esters and squalene are unique to sebum and not produced as final products anywhere else in the body.[5] Sapienic acid is a sebum fatty acid that is unique to humans, and is implicated in the development of acne.[15] Sebum is odorless, but its breakdown by bacteria can produce strong odors.[16]

estrogens have been shown to inhibit secretion.[17] Dihydrotestosterone acts as the primary androgen in the prostate and in hair follicles.[18][19]

Immune function and nutrition

Sebaceous glands are part of the body's

microbes that might penetrate the skin.[20] The pH of the skin is between 4.5 and 6.2,[21] an acidity that helps to neutralize the alkaline nature of contaminants.[22] Sebaceous lipids help maintain the integrity of the skin barrier[10][23][24] and supply vitamin E to the skin.[25]

Unique sebaceous glands

During the last three months of

fetal development, the sebaceous glands of the fetus produce vernix caseosa, a waxy white substance that coats the skin to protect it from amniotic fluid.[26]

The

areolar glands are in the areola that surrounds the nipple in the female breast. These glands secrete an oily fluid that lubricates the nipple, and also secrete volatile compounds that are thought to serve as an olfactory stimulus for the newborn. During pregnancy and lactation these glands, also called Montgomery's glands, become enlarged.[27]

tarsal plates
of the eyelids.

milia (milk spots).[29]

viscous and have a high lipid content, which provides good lubrication.[30]

Clinical significance

Conditions of sebaceous glands

Sebaceous glands are involved in skin problems such as

acne and keratosis pilaris. In the skin pores, sebum and keratin can create a hyperkeratotic plug called a comedo
.

Acne

Main article: Acne

teenagers, and is thought to relate to an increased production of sebum due to hormonal factors. The increased production of sebum can lead to a blockage of the sebaceous gland duct. This can cause a comedo (commonly called a blackhead or a whitehead), which can lead to infection, particularly by the bacteria Cutibacterium acnes. This can inflame the comedones, which then change into the characteristic acne lesions. Comedones generally occur on the areas with more sebaceous glands, particularly the face, shoulders, upper chest and back. Comedones may be "black" or "white" depending on whether the entire pilosebaceous unit, or just the sebaceous duct, is blocked.[31] Sebaceous filaments
—innocuous build-ups of sebum—are often mistaken for whiteheads.

There are many treatments available for acne from reducing sugars in the diet, to medications that include antibiotics, benzoyl peroxide, retinoids, and hormonal treatments.[31] Retinoids reduce the amount of sebum produced by the sebaceous glands.[32] Should the usual treatments fail, the presence of the Demodex mite could be looked for as the possible cause.[33]

Other

Other conditions that involve the sebaceous glands include:

  • Seborrhoea refers to overactive sebaceous glands, a cause of oily skin[5] or hair.[16]
  • Sebaceous hyperplasia, referring to excessive proliferation of the cells within the glands, and visible macroscopically as small papules on the skin, particularly on the forehead, nose and cheeks.[34]
  • newborn infants, seborrhoea dermatitis can occur as cradle cap
    .
  • Seborrheic-like psoriasis (also known as "Sebopsoriasis",[36] and "Seborrhiasis") is a skin condition characterized by psoriasis with an overlapping seborrheic dermatitis.[3]: 193 
  • tumour—which may, however, in rare cases be a precursor to a cancer syndrome known as Muir–Torre syndrome.[5]
  • Sebaceous carcinoma, an uncommon and aggressive cutaneous tumour.[37]
  • pilar cyst, though neither of these contain sebum, only keratin and do not originate in the sebaceous gland and so are not true sebaceous cysts. A true sebaceous cyst is relatively rare and is known as a steatocystoma.[38]
  • Nevus sebaceous, a hairless region or plaque on the scalp or skin, caused by an overgrowth of sebaceous glands. The condition is congenital and the plaque becomes thicker into adulthood.[39]
  • cutaneous condition characterized by an overgrowth of sebaceous glands.[36]

History

The word sebaceous, meaning 'consisting of sebum', was first termed in 1728 and comes from the Latin for 'tallow'.

apthous ulcers, noting that "these glands naturally [secrete] a viscous humour, which puts on various colours and consistencies... in its natural state is very mild, balsamic, and intended to wet and lubricate the mouth".[41]: 85–86  In The Principles of Physiology 1834, Andrew Combe noted that the glands were not present in the palms of the hands or soles of the feet.[42]

Other animals

Example of a gular gland in a male black bonneted bat[43]
Example of a gular gland in a male black bonneted bat[43]

The preputial glands of mice and rats are large modified sebaceous glands that produce pheromones used for territorial marking.[5] These and the scent glands in the flanks of hamsters have a similar composition to human sebaceous glands, are androgen responsive, and have been used as a basis for study.[5] Some species of bat, including the Mexican free-tailed, have a specialized sebaceous gland occurring on the throat called a "gular gland".[44] This gland is present more frequently in males than females, and it is hypothesized that the secretions of the gland are used for scent-marking.[45]

autosomal recessively inherited. It has also been described in cats, and one report describes this condition in a rabbit. In these animals, it causes hair loss, though the nature and distribution of the hair loss differs greatly.[46]

See also

References

  1. ^ "Hair follicle sebaceous gland: MedlinePlus Medical Encyclopedia Image". medlineplus.gov. Archived from the original on 6 June 2023. Retrieved 6 June 2023.
  2. PMID 29484100
    .
  3. ^
    ISBN 978-0-7216-2921-6
    .
  4. ^
    ISBN 978-0-443-06850-8
    .
  5. ^
    PMID 17975220
    .
  6. ^
    PMID 15191536
    .
  7. ^
    PMID 2648418
    .
  8. ^
    S2CID 8504408. Archived
    from the original on 17 November 2019. Retrieved 29 June 2019.
  9. ^ Dellmann's textbook of veterinary histology (405 pages), Jo Ann Coers Eurell, Brian L. Frappier, 2006, p.29, weblink: Books-Google-RTOC Archived 24 February 2024 at the Wayback Machine.
  10. ^
    PMID 15556719
    .
  11. PMID 11385091
    .
  12. ^ Victor Eroschenko, diFiore's Atlas of Histology with functional correlations, Lippincott Williams & Wilkins, 10th edition, 2005. p. 41
  13. ISBN 978-0-19-856878-0
    .
  14. ^
    PMID 15220349
    .
  15. ISBN 978-0-8247-2971-4
    .
  16. ^
    ISBN 978-1-84184-194-6. Archived
    from the original on 24 February 2024. Retrieved 7 December 2016.
  17. PMID 5793140
    .
  18. PMID 18423697
    .
  19. ISBN 978-0-521-24122-9
    .
  20. ISBN 978-3-936072-64-8
    . Retrieved 19 June 2012.
  21. S2CID 3065931
    .
  22. PMID 8573921. Archived from the original
    (PDF) on 1 March 2011.
  23. PMID 20082943
    .
  24. S2CID 10119536. Archived
    from the original on 9 January 2020. Retrieved 17 October 2011.
  25. PMID 10594744
    .
  26. PMID 18474083
    .
  27. PMID 19851461
    .
  28. PMID 15106913
    .
  29. ISBN 978-0-19-856878-0
    .
  30. PMID 9433685
    .
  31. ^
    ISBN 978-0-7020-3085-7
    .
  32. PMID 6451637
    .
  33. PMID 22135150
    .
  34. ISBN 978-0-7216-2921-6
    .
  35. PMID 23806151
    .
  36. ^
    ISBN 978-1-4160-2999-1
    .
  37. PMID 7601925
    .
  38. ISBN 978-0-7216-9003-2
    .
  39. PMID 16403388. Archived
    from the original on 2 October 2012. Retrieved 21 November 2019.
  40. ^ Harper, Douglas. "Sebaceous". Etymology Online. Archived from the original on 1 March 2017. Retrieved 5 April 2014.
  41. ^ a b c d Astruc, Jean (1746). A General and Compleat Treatise on All the Diseases Incident to Children. J. Nourse. p. 3. Sebaceous glands.
  42. PMID 13598929
    .
  43. ^ Dobson, G. E. (1878). Catalogue of the Chiroptera in the collection of the British Museum. Order of the Trustees.
  44. S2CID 3093610
    .
  45. ^ Heideman, P. D., Erickson, K. R., & Bowles, J. B. (1990). Notes on the breeding biology, gular gland and roost habits of Molossus sinaloae (Chiroptera, Molossidae) Archived 21 October 2021 at the Wayback Machine. Zeitschrift für Säugetierkunde, 55(5), 303-307.
  46. ISBN 978-0-8138-1934-1. Archived
    from the original on 24 February 2024. Retrieved 25 September 2016.

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Sebaceous_gland&oldid=1218910564#Sebum"
This page is based on the copyrighted Wikipedia article: Sebum. Articles is available under the CC BY-SA 3.0 license; additional terms may apply.Privacy Policy