Sebaceous gland

Sebaceous gland
Schematic view of a hair follicle with sebaceous gland.
Cross-section of all skin layers.A hair follicle with associated structures. (Sebaceous gland labeled at center left.)
Latin	glandula sebacea
Gray's	subject #234 1069
MeSH	Sebaceous+glands
Dorlands/Elsevier	g_06/12392642

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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.

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.

Sebum

Sebaceous glands secrete an oily 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 if it is not washed for several days. Earwax is partly composed of sebum.

Sebum acts to protect and waterproof hair and skin, and keep them from becoming dry, brittle, and cracked. It can also inhibit the growth of microorganisms on skin. This is what makes the face oily.

Composition

The composition of sebum varies from species to species; in humans, the lipid content is as follows:

Percent composition	Substance
25%	wax monoesters
41%	triglycerides
16%	free fatty acids
12%	squalene

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 however normal, 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.

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 images

• 

  Sagittal section through the upper eyelid.

• 

  A hair follicle with associated structures.

External links

• Histology at Boston University 08801loa - "Integument: scalp"

Cost Effectiveness of Sebaceous gland

| group5 = Clinical Trials Involving Sebaceous gland | list5 = Ongoing Trials on Sebaceous gland at Clinical Trials.gov • Trial results on Sebaceous gland • Clinical Trials on Sebaceous gland at Google

| group6 = Guidelines / Policies / Government Resources (FDA/CDC) Regarding Sebaceous gland | list6 = US National Guidelines Clearinghouse on Sebaceous gland • NICE Guidance on Sebaceous gland • NHS PRODIGY Guidance • FDA on Sebaceous gland • CDC on Sebaceous gland

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| group8 = Pharmacology Resources on Sebaceous gland | list8 = AND (Dose)}} Dosing of Sebaceous gland • AND (drug interactions)}} Drug interactions with Sebaceous gland • AND (side effects)}} Side effects of Sebaceous gland • AND (Allergy)}} Allergic reactions to Sebaceous gland • AND (overdose)}} Overdose information on Sebaceous gland • AND (carcinogenicity)}} Carcinogenicity information on Sebaceous gland • AND (pregnancy)}} Sebaceous gland in pregnancy • AND (pharmacokinetics)}} Pharmacokinetics of Sebaceous gland •

| group9 = Genetics, Pharmacogenomics, and Proteinomics of Sebaceous gland | list9 = AND (pharmacogenomics)}} Genetics of Sebaceous gland • AND (pharmacogenomics)}} Pharmacogenomics of Sebaceous gland • AND (proteomics)}} Proteomics of Sebaceous gland

| group10 = Newstories on Sebaceous gland | list10 = Sebaceous gland in the news • Be alerted to news on Sebaceous gland • News trends on Sebaceous gland</small>

| group11 = Commentary on Sebaceous gland | list11 = Blogs on Sebaceous gland

| group12 = Patient Resources on Sebaceous gland | list12 = Patient resources on Sebaceous gland • Discussion groups on Sebaceous gland • Patient Handouts on Sebaceous gland • Directions to Hospitals Treating Sebaceous gland • Risk calculators and risk factors for Sebaceous gland

| group13 = Healthcare Provider Resources on Sebaceous gland | list13 = Symptoms of Sebaceous gland • Causes & Risk Factors for Sebaceous gland • Diagnostic studies for Sebaceous gland • Treatment of Sebaceous gland

| group14 = Continuing Medical Education (CME) Programs on Sebaceous gland | list14 = CME Programs on Sebaceous gland

| group15 = International Resources on Sebaceous gland | list15 = Sebaceous gland en Espanol • Sebaceous gland en Francais

| group16 = Business Resources on Sebaceous gland | list16 = Sebaceous gland in the Marketplace • Patents on Sebaceous gland

| group17 = Informatics Resources on Sebaceous gland | list17 = List of terms related to Sebaceous gland

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