▶ Previous Artlcle: #5-2. Laser in Clinical Medicine
Melanocytes arise from the neural crest and are scattered in the basal cell layer. The ratio of melanocytes to basal keratinocytes is about 1:10.
It has a number of dendrites and forms an epidermal melanin unit by contacting an average of 36 keratinocytes per melanocyte.
At birth, there are about 1,200 melanocytes per cm2, which decreases by 6-8% every 10 years, leaving about 600 per cm2 at above 80 years of age.
Melanocytes produce melanin that leaves pigmentation on the skin, which protects the skin from UV rays.
Melanin is divided into eumelanin and pheomelanin. When eumelanin is contained, the skin and hair appear to be brown or black.
When pheomelanin is contained, white skin color and yellow or reddish brown hair appear.
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The number of melanocytes is constant. The difference in the skin color whether it is lighter or darker is attributable to the presence of eumelanin orpheomelanin,melanosome density, size, melanization level, and distribution.
As shown in the figure, adrenergic receptor, MC1R, and c-kitare activated when affected by UV rays and hormones.
As a result, MITF andtyrosinase are activated, thereby causing the increase of melanin synthesis in tyrosine.
- To be continued
