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, melanocytes are only triggered by ultraviolet rays, thus requiring sun exposure in order to tan. In other people, the melanocytes constantly produce melanin and this can also be enhanced by sun exposure[1] (http://www.yourperfectan.com/htm/yourtan/skintype.htm)[2] (http://www.perfectimage85.com/TanGuide/TGuidemain.htm).
The typical density of melanocytes is between 1000 and 2000 cells per square millimeter of skin, comprising between 5-10% of cells in the skin. 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.
Embryologically, melanocytes come from the neural crest. This is completely different to the surrounding skin cells (keratinocytes). 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: Melanocytes originate in the neural crest and migrate to the basal layer of the epidermis and the hair matrices.
The failure of melanocytes to migrate to these locations explains the association of congenital white spotting of the skin (piebaldism) with heterochromia (the juxtaposition of different colors) in the iris as well as congenital deafness in Waardenburg syndrome.
Malignancy: Melanoma is a malignant tumor that arises from a mutant melanocyte.
Melanocytes are cells located in the bottom layer, the basal lamina, of the skin'sepidermis and in the middle layer of the eye, the uvea.
The difference in skin color between fair people and dark people is due not to the number of melanocytes in their skin, but to the melanocytes' level of activity.
All melanocytes have the capacity to migrate widely in the embryo, and therefore a cancer of a melanocyte, a melanoma, will spread (metastasize) very easily.
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