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Why do peoples hair change colors when the get older?
Question Date: 2009-02-06
Answer 1:

The color in hair comes from melanin, a class of pigments that is produced by cells called melanocytes. The melanocytes that affect hair color are found in and around the bulb at the base of the hair follicle. Melanocytescontain organelles called melanosomes that produce the two forms of melanin that give hair its color; eumelanin, which is brown-black; and pheomelanin, which is a red-brown-blond. During follicular growth, melanocytes secret emelanosomes into keratinocyte cells (which form the uppermost layer of skin and produce keratin, a tough protein that is the primary constituent of hair, nails and skin). The melanin is incorporated into the hair follicles, giving it color. The process of hair graying (officially called achromotrichia) is a common phenomenon that affects most people, usually starting in their 30s or 40s. Grey (and eventually white) hair starts to appear because the melanocytes slow, and ultimately stop, producing melanin that can be incorporated into the hair follicle. The onset of achromotrichia appears to be hereditary (having a genetic basis). So far, two genes, Bcl2and Bcl-w, have been singled out as being in control of the graying process.It appears that these genes regulate cell-death in the melanocytic stem cells found in the base of the hair follicle. In early life, these stemcells produce new, fully functioning melanocytes, but once the stem cellsdie, there is no new source of melanin-producing melanocytes.

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