| Sebaceous gland | |
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| Schematic view of a hair follicle with sebaceous gland. | |
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| 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 |
The sebaceous glands are glands found in the skin of mammals. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. the Peripheral organs of the Special senses the organs of Taste ( Peripheral gustatory or Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group A gland is an organ in an animal's body that synthesizes a substance for release such as Hormones or Breast milk, often into the Bloodstream The skin is the outer covering of living tissue of an animal (or plant Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands
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Locations and morphology
A branched type of acinar gland, these glands exist in humans throughout the skin except in the palms of the hands, lips and soles of the feet. In contrast to Tubular glands, in the second main variety of gland the secretory portion is enlarged and the lumen variously increased in size The hands ( med / lat: manus pl manūs are the two intricate prehensile multi- Fingered body parts normally located at the end of each arm of a The sole is the bottom of the human Foot. Anatomically the sole of the foot is referred to as the plantar aspect.
Sebaceous glands can usually be found in hair-covered areas, where they are connected to hair follicles. A hair follicle is part of the Skin that grows Hair by packing old cells together 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. An eyelid is a thin fold of skin that covers and protects an Eye. The penis (plural penises, penes The labia minora (singular labium minus) or nymphae are two longitudinal Cutaneous folds on the human Vulva. In its most general form a nipple is a Structure from which a fluid emanates Here, the sebum traverses ducts which terminate in sweat pores on the surface of the skin. The inner surface of the lip contains sebaceous glands also, here they are common as Fordyce's spots. Fordyces spot closeupjpg|thumb|Close-up of Fordyce's spots on a penis
At the rim of the eyelids, meibomian glands are a specialized form of sebaceous gland. The meibomian glands (or tarsal glands) are a special kind of Sebaceous glands at the rim of the Eyelids responsible for the supply of Sebum, They secrete sebum into the tears coating the eye, to slow evaporation. Tears are the liquid product of a process of lacrimation to clean and lubricate the Eyes The word lacrimation may also be used in a medical or literary sense Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain
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. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water Tallow is a rendered form of Beef or Mutton Fat, processed from Suet. Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble In the glands, sebum is produced within specialized cells and is released as these cells burst; sebaceous glands are thus classified as holocrine glands. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Holocrine is a classification of Exocrine glands in the study of Histology. Sebum itself is odorless, but its bacterial breakdown can produce odors. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Sebum is one cause of some people experiencing "oily" hair or skin if not washed for several days. Earwax is partly composed of sebum. Earwax, also known by the Medical term cerumen, is a yellowish waxy substance secreted in the Ear canal of Humans and many other
Sebum acts to protect and waterproof hair and skin, and keep them from becoming dry, brittle, and cracked. Hair is a keratinised protein filament that grows through the epidermis from follicles deep within the Dermis. It can also inhibit the growth of microorganisms on skin.
Composition
The composition of sebum varies from species to species; in humans, the lipid content is as follows:[1]
| 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. Esters are a class of Chemical compounds and Functional groups Esters consist of an inorganic or organic Acid in which at least (more properly known as, TAG or triacylglyceride) is Glyceride in which the Glycerol is Esterified with three Fatty acids It is the In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which Squalene is a natural Organic compound originally obtained for commercial purposes primarily from Shark liver oil, though there are botanic sources as well including A fetus (or foetus or fœtus) is a developing Mammal or other Viviparous Vertebrate, after the Embryonic stage and For the Nirvana album see In Utero. In utero is a Latin term literally meaning "in the Uterus " Vernix, also known as Vernix caseosa, is the waxy or " cheesy " white substance found coating the Skin of Newborn humans
The activity of the sebaceous glands increases during puberty because of heightened levels of androgens. Androgen is the generic term for any natural or synthetic compound usually a Steroid Hormone, that stimulates or controls the development and maintenance of masculine In males, sebaceous glands begin to appear predominantly on the penis during and after puberty. The penis (plural penises, penes This is normal, however, and not to be confused with an STD. A sexually transmitted disease ( STD) or venereal disease ( VD) is an illness that has a significant probability of transmission between Humans In females, they appear predominantly in the labia minora. The labia minora (singular labium minus) or nymphae are two longitudinal Cutaneous folds on the human Vulva.
Pathology
Sebaceous glands are involved in skin problems such as acne and keratosis pilaris. Acne vulgaris (commonly called acne) is a Skin disease caused by changes in the Pilosebaceous units (skin structures consisting of a Hair follicle Keratosis pilaris (KP also follicular keratosis is a very common genetic follicular condition that is manifested by the appearance of rough bumps on the skin The prescription drug isotretinoin significantly reduces the amount of sebum produced by the sebaceous glands, and is used to treat acne. Isotretinoin ( INN) (aɪsoʊtrɨˈtɪnoʊɨn or /ˌaɪsoʊtrɨˈtɪnoʊɨn/ is a Medication used for the treatment of severe 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. Anabolic steroids, or anabolic-androgenic steroids ( AAS) are a class of Steroid hormones related to the hormone Testosterone. Bodybuilding is the process of maximizing Muscle hypertrophy. Muscle hypertrophy is a scientific term for the growth and increase of the size of muscle cells [2]
A blocked sebaceous gland can result in a sebaceous cyst. A sebaceous cyst (a form of Trichilemmal Cyst) is a closed sac or Cyst below the surface of the skin that has a lining that resembles the
One condition involving enlarged sebaceous glands is known as sebaceous hyperplasia. Sebaceous hyperplasia is a disorder of the Sebaceous glands in which they become enlarged Another common condition is seborrheic dermatitis. Seborrhoeic Eczema (also Seborrheic dermatitis AmE, seborrhea) is a skin disorder affecting the scalp face and trunk causing scaly flaky
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. 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 Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled
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. Demodex is a Genus of tiny parasitic Mites that live in or near Hair follicles of Mammals About 65 species of Demodex
The preputial glands of mice and rats are large modified sebaceous glands that produce pheromones. Preputial glands are Exocrine glands that are located in front of the Genitals of some Mammals and produce Pheromones The preputial glands of female A mouse (plural mice) is a small Animal that belongs to one Rats are various medium sized long-tailed Rodents of the superfamily Muroidea A pheromone (from Greek φέρω phero "to bear" + ‘ορμόνη " Hormone " is a Chemical that triggers a natural
Additional images
 Sagittal section through the upper eyelid. |
 A hair follicle with associated structures. |
References
- ^ Jeffrey B. Cheng and David W. Russell. Mammalian Wax Biosynthesis II: Expression Cloning of Wax Synthase cDNAs Encoding a Member of the Acyltransferase Enzyme Family, J Biol Chem. 2004 Sep 3;279(36):37798-37807. p. 3 (Introduction) PMID 15220349 Fulltext
- ^ Abuse Of Anabolic Steroids Causes Acne In Bodybuilders, by Medinda. com
External links
- Histology at BU 08801loa - "Integument: scalp"
Dictionary
sebaceous gland
-noun
- (anatomy) A gland of the skin which secretes an oily substance, sebum, usually into a hair follicle near the surface of the skin.
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