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
Famous quotes containing the words human and/or differences:
“A person unlearns arrogance when he knows he is always among worthy human beings; being alone fosters presumption. Young people are arrogant because they always associate with their own peers, those who are all really nothing but who would like to be very important.”
—Friedrich Nietzsche (1844–1900)
“I don’t know what immutable differences exist between men and women apart from differences in their genitals; perhaps there are some other unchangeable differences; probably there are a number of irrelevant differences. But it is clear that until social expectations for men and women are equal, until we provide equal respect for both men and women, our answers to this question will simply reflect our prejudices.”
—Naomi Weisstein (b. 1939)