Melanin
: A skin pigment (substance that gives the skin its color). Dark-skinned people have more melanin than light- skinned people. Melanin also acts as a sunscreen and protects the skin from ultraviolet light. Melanin is produced by cells called melanocytes. It provides some protection again skin damage from the sun, and the melanocytes increase their production of melanin in response to sun exposure. Freckles, which occur in people of all races, are small, concentrated areas of increased melanin production.
* * *
Any of the dark brown to black polymers of indole-5,6-quinone and/or 5,6-dihydroxyindole 2-carboxylic acid that normally occur in the skin, hair, pigmented coat of the retina, and inconstantly in the medulla and zona reticularis of the adrenal gland. M. may be formed in vitro or biologically by oxidation of l-tyrosine or l-tryptophan, the usual mechanism being the enzymatic oxidation of l-tyrosine to 3,4-dihydroxy-l-phenylalanine (dopa) and dopaquinone by monophenol monooxygenase, and the further oxidation (probably spontaneous) of this intermediate to m.. Cf.:eumelanin, pheomelanin. SYN: melanotic pigment. [G. melas (melan-), black]
- artificial m., factitious m. SYN: melanoid.

* * *

mel·a·nin 'mel-ə-nən n any of various black, dark brown, reddish brown, or yellow pigments of animal or plant structures (as skin, hair, the choroid, or a raw potato when exposed to air) esp any of numerous animal pigments that are essentially polymeric derivatives of indole formed by enzymatic modification of tyrosine

* * *

n.
a dark-brown to black pigment occurring in the hair, the skin, and in the iris and choroid layer of the eyes. Melanin is contained within special cells (chromatophores or melanophores) and is produced by the metabolism of the amino acid tyrosine. Production of melanin by melanocytes in the epidermis of the skin is increased by the action of sunlight (producing tanning), which protects the underlying skin layers from the sun's radiation.

* * *

mel·a·nin (melґə-nin) [Gr. melas black] any of several closely related dark, amorphous pigments of the skin, hair, and various tumors, of the choroid coat of the eye and of the brain (neuromelanin, q.v.). Melanins are produced by polymerization of oxidation products of tyrosine and dihydroxyphenyl compounds, and contain carbon, hydrogen, nitrogen, oxygen, and often sulfur. See also eumelanin and pheomelanin.

Medical dictionary. 2011.

Look at other dictionaries:

  • Melanin — Mel a*nin, n. [Gr. me las, me lanos, black.] (Physiol.) A black pigment found in the pigment bearing cells of the skin (particularly in the skin of the negro), in the epithelial cells of the external layer of the retina (then called {fuscin}), in …   The Collaborative International Dictionary of English

  • melanin — melanin. См. меланин. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Melanin — Melanin, das schwarze Pigment, welches sich als Überzug auf der Choroïdea des Auges findet. Ob das Pigment in den schwarzen Bronchialdrüsen, dem Rete Malpighii der Neger, in der Melanose (s.d.) u. dem schwarzen Serum des Lungengewebes mit diesem… …   Pierer's Universal-Lexikon

  • Melanīn — Melanīn, schwarzer Farbstoff in der Netzhaut des Auges (Augenschwarz), in der Haut des Negers, in den Pigmentierungen der Lungen und Bronchialdrüsen Erwachsener, im Bauchfell vieler Fische, bei Amphibien, in der Tinte der Sepien, in den… …   Meyers Großes Konversations-Lexikon

  • Melanin — Melanīn, Ophthalmomelanin, Augenschwarz, ein schwarzer Farbstoff in der Gefäßhaut des Auges, der Haut des Negers, der Tinte der Sepien und krankhaften Geschwülsten, eisenreich …   Kleines Konversations-Lexikon

  • Melanin — Melanin, braunes oder schwarzes höher molekulares Pigment; bei vielen Tiergruppen vorhanden; aus der Aminosäure Tyrosin gebildet; kommt bei Wirbeltieren in den Melanocyten der Haut vor und schützt Oberhaut und Augen vor zu starker UV Strahlung.… …   Deutsch wörterbuch der biologie

  • melanin — dark brown or black pigment found in animal bodies, 1832, Modern Latin, with chemical suffix IN (Cf. in) (2); first element from Gk. melas (gen. melanos) black, from PIE root *mel dark, soiled, dirty (Cf. Skt. malinah dirty, stained, black, Lith …   Etymology dictionary

  • melanin — melànīn m <G melanína> DEFINICIJA fiziol. tamnosmeđi do crni pigment u čovjeka i životinja; daje boju koži, kosi i očima, štiti od štetnog djelovanja Sunčevih zraka ETIMOLOGIJA grč. mélas: crn + in …   Hrvatski jezični portal

  • melanin — ► NOUN ▪ a dark pigment in the hair and skin, responsible for tanning of skin exposed to sunlight. ORIGIN from Greek melas black …   English terms dictionary

  • melanin — [mel′ə nin] n. [ MELAN(O) + IN1] a brownish black pigment found in skin, hair, and other animal or plant tissues …   English World dictionary

  • Melanin — Not to be confused with melamine, melatonin, or Melanotan (disambiguation). Melanin pigment (dark granular material center of image) in a pigmented melanoma. Pap stain. Melanin …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”