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Illustration of a melanocyte Micrograph of melanocytes in the epidermis. Through a process called melanogenesis, melanocytes produce melanin, which is a pigment found in the skin, eyes, hair, nasal cavity, and inner ear. This melanogenesis leads to a long-lasting pigmentation, which is in contrast to the pigmentation that originates from ...
Poliosis circumscripta, commonly referred to as a "white forelock", is a condition characterized by localized patches of white hair due to a reduction or absence of melanin in hair follicles. Although traditionally associated with the scalp, poliosis can affect any hairy area on the body, including eyebrows, eyelashes, and beards.
Inside the melanocytes, tyrosine is converted into L-DOPA and then L-dopaquinone, which in turn is formed into pheomelanin or eumelanin. [6] Different hair color phenotypes arise primarily as a result of varying ratios of these two pigments in the human population, [5] although Europeans show the greatest range in pigmentation overall. [7]
Albinism occurs when melanocytes produce little melanin. This albino girl is from Papua New Guinea. In humans, melanin is the primary determinant of skin color. It is also found in hair, the pigmented tissue underlying the iris of the eye, and the stria vascularis of the inner ear.
Piebaldism refers to the absence of mature melanin-forming cells (melanocytes) in certain areas of the skin and hair. It is a rare autosomal dominant disorder of melanocyte development. [ 2 ] : 867 Common characteristics include a congenital white forelock , scattered normal pigmented and hypopigmented macules and a triangular shaped ...
The change in hair colour occurs when melanin ceases to be produced in the hair root and new hairs grow in without pigment. The stem cells at the base of hair follicles produce melanocytes, the cells that produce and store pigment in hair and skin. The death of the melanocyte stem cells causes the onset of greying. It remains unclear why the ...
Hair acquires pigment from melanocytes in the root bulb, which deposit melanosomes into the growing hair structure. A critical step in the production of melanins is the catalysis of tyrosine by an enzyme called tyrosinase , producing dopaquinone.
This overproduction causes depletion of the melanocyte stem cells which are required to produce melanin, the pigment responsible for hair color. [2] Premature greying of hair has been observed with greater frequency among certain families, suggesting a familial predisposition for the condition.