Melanocytes are cells located in the bottom layer of the skin's epidermis. With a process called melanogenesis, they produce melanin, a pigment in the skin, eyes, and hair. In Caucasians, and some Asians, melanocytes are never triggered except by ultraviolet rays, thus requiring sun exposure in order to tan. Amongst darker peoples, the melanocytes constantly produce melanin and this can also be enhanced by sun exposure[1][2]. It has been suggested that extracellular be merged into this article or section. ... Epidermis is the outermost layer of the skin. ... Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks or their mixed copolymers. ... A section of Human Skin In zootomy and dermatology, skin is an organ of the integumentary system made up of a layer of tissues that guard underlying muscles and organs. ... This article or section does not cite its references or sources. ... Young Girl Fixing her Hair, by Sophie Gengembre Anderson Hair is a filamentous outgrowth skin found only in mammals. ... This article does not cite its references or sources. ... The term Asian can refer to something or someone from Asia. ... Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays. ...

The typical density of melanocytes is between 1000 and 2000 cells per square mm of skin, comprising between 5-10% of cells in the skin. Although the size may vary, the typical size of a melanocyte is 7 micrometers in length. The difference between fair people and dark people is not the number of melanocytes, but how active the melanocytes are.

Albinos lack an enzyme, tyrosinase, that is required for melanocytes to produce melanin. Albinism is a genetic condition resulting in a lack of pigmentation in the eyes, skin and hair. ... Tyrosinase (Catechol Oxidase) is an enzyme that catalyses the oxidation of phenols (such as tyrosine) and is widespread in plants and animals. ...

Embryologically, melanocytes come from the neural crest. This is completely different to the surrounding skin cells (keratinocytes) and means that all melanocytes had the capacity to migrate widely in the embryo. This fact also means that a cancer of a melanocyte, a melanoma, will spread (metastasize) very easily. For this reason melanomas are often fatal, and when being removed a lot of surrounding tissue needs to be taken as well. Embryology is the branch of developmental biology that studies embryos and their development. ... The neural crest, a component of the ectoderm, is one of several ridgelike clusters of cells found on either side of the neural tube in vertebrate embryos. ... The keratinocyte is the major cell type of the epidermis, making up about 90% of epidermal cells. ... Skin cancer, close-up of level IV melanoma Melanoma is a malignant tumour of melanocytes . ... Metastasis (Greek: change of the state) is the spread of cancer from its primary site to other places in the body. ...

Melanin is initiated by either MSH (melanocyte-stimulating hormone), ACTH (another hormone) or ultraviolet light. Once made, melanin is then stored in “the warehouses”. These are the arm like structures called dendrites. From there they are shipped to the keratinocyte. Melanocyte-stimulating hormone (MSH) is a peptide hormone produced by cells in the intermediate lobe of the pituitary gland. ...

Melanogenesis

When ultraviolet rays penetrate the skin and damage DNA; thymidine dinucleotides (pTpT) fragments from damaged DNA will trigger release of the hormone alpha-MSH, which can then bind to melanocytes to cause them produce melanin. Melanin vesicles from the melanocytes are then transferred to surrounding keratinocytes. The skin will then be darker when the keratinocytes which have been filled with melanin move toward the skin surface. The general structure of a section of DNA Deoxyribonucleic acid (DNA) is a nucleic acid —usually in the form of a double helix— that contains the genetic instructions specifying the biological development of all cellular forms of life, and most viruses. ... A hormone (from Greek horman - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ... Melanocyte-stimulating hormone (MSH) is a peptide hormone produced by cells in the intermediate lobe of the pituitary gland. ... Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks or their mixed copolymers. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ... The keratinocyte is the major cell type of the epidermis, making up about 90% of epidermal cells. ...

See also

• Chromatophore (the cells that allow octopuses and cuttlefish to change their color rapidly)

Chromatophore is the collective term for pigment containing and light reflecting cells found in amphibians, fish, reptiles, crustaceans and cephalopods. ... Families 14 in two suborders, see text. ... Families Sepiadariidae Sepiidae Cuttlefish are animals of the order Sepiida, and are marine cephalopods, small relatives of squids and nautilus. ...

External links

• The IFPCS presidential lecture: a chemist's view of melanogenesis