Human Differences
Typically, between 1000 and 2000 melanocytes per square millimeter of skin are found. Melanocytes comprise from 5% to 10% of the cells in the basal layer of epidermis. Although their size can vary, melanocytes are typically 7 μm in length.
The difference in skin color between lightly and darkly pigmented individuals is due not to the number (quantity) of melanocytes in their skin, but to the melanocytes' level of activity (quantity and relative amounts of eumelanin and pheomelanin). This process is under hormonal control, including the MSH and ACTH peptides that are produced from the precursor proopiomelanocortin.
Albinos lack an enzyme called tyrosinase. Tyrosinase is required for melanocytes to produce melanin from the amino acid tyrosine.
Read more about this topic: Melanocyte
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