Human sebum, as it leaves the sebaceous gland, contains squalene, cholesterol, cholesterol esters, wax esters, and triglycerides. Sebaceous glands are regulated by several molecules, among them androgens and retinoids. Human sebaceous glands are multilobular structures of epithelial origin Your MyAccess profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. This div only appears when the trigger link is hovered over.
Otherwise it is hidden from view. Forgot Username? About MyAccess If your institution subscribes to this resource, and you don't have a MyAccess Profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.
Learn More. Sign in via OpenAthens. Sign in via Shibboleth. AccessBiomedical Science. AccessEmergency Medicine. Case Files Collection. Sebaceous Gland: Schematic view of a hair follicle with sebaceous gland. Sebaceous glands are involved in numerous conditions. During puberty, various hormones cause them to produce a lot of sebum and this therefore contributes to oily skin. If a duct of a sebaceous gland is clogged with sebum, a whitehead results.
If this material is allowed to dry and oxidize, it will become darker, forming a blackhead. If a sebaceous gland becomes infected, moderate and severe forms of acne are the result. The glands lining the ear canal that produce earwax cerumen are called ceruminous glands. When they contract, they increase the amount of sweat produced i. The sweat glands are simple tubular exocrine glands that are found in the superficial hypodermis bordering on the dermis. They discharge their contents onto the surface of the skin via coiled secretory ducts see the diagram opposite.
The ducts open out onto epidermal ridges at a sweat pore. They can be further classified as merocrine eccrine glands. They secrete a watery fluid which is hypotonic to plasma its evaporation is important for thermoregulation. Sweat contains water, sodium, potassium, chloride, urea ammonia and lactic acid. These include the meibomian glands of the eyelids and the Fordyce spots of the lips and genitals.
Sebaceous glands work in tandem with the sweat-producing eccrine glands to regulate body temperature. In hot conditions, the excreted sebum mixes with sweat to slow the rate of evaporation. In cold temperatures, the sebum will contain more lipids to shield the hair and skin from moisture that can facilitate heat loss.
In addition to maintaining moisture and regulating temperatures, sebum contains squalene and other substances that prevent bacteria, fungi, and other microorganisms from causing infection. Sebaceous glands are first visible between weeks 13 and 16 of fetal development and emerge from the same stem cells that give rise to the outermost layer of skin, called the epidermis.
Following birth, the activity of the glands will gradually decrease and become nearly inactive between the ages of two and six. It is after this period that the production of sebum will steadily increase, reaching an apex during puberty as boys and girls both experience a sudden spike in male hormones androgens.
Sebum production tends to slow by around the age of 20 and continues diminishing the older we get. As this occurs, the skin can become drier and lose elasticity. These changes, referred to sebostasis , tend to occur in tandem with decreases in androgen production.
The loss of moisture, combined with the depletion of collagen and keratin, can lead to characteristically dry skin xerosis cutis and brittle hair. The condition most of us associate with the sebaceous glands is pimples. While the pores of the skin are great self-cleaning machines, any accumulation of dirt or debris can combine with sebum to create a glue-like compound that can seal the entryway. Once blocked, bacteria like Staphylococcus aureus and Propionibacterium acnes can begin to multiply and thrive, leading to the development of a pus-filled bump we recognize as a pimple.
This photo contains content that some people may find graphic or disturbing. Pimples are medically referred to as acne vulgaris. Those that are severe and consolidate into boil-like pustules are known as cystic acne.
Teenagers tend to be most vulnerable to pimples because the changes in hormones not only increase the volume of sebum but the concentration of wax esters within it, leading to thicker, gummier oils.
Treatments include antibiotics , benzoyl peroxide , retinoids , and anti-androgen drugs such as spironolactone. While pimples may be the result of hormonal imbalances, they can also be caused by steroids, contraceptives, and immunosuppressant drugs. Pimples can also be mistaken for other conditions such as folliculitis , lupus miliaris disseminates faciei , and Demodex mites a microscopic, eight-legged arachnid that lives in or near follicles.
0コメント