B. Pigmentation System: Skin color is conferred mainly by the pigments melanin and carotene, the thickness of the epidermis, the number of dermal blood vessels, and the color of the blood in those vessels.
1. Melanins contribute to skin, eye, and hair color. Synthesized by melanocytes, they include the dark brown pigment eumelanin, found in the epidermis, iris, and brown and black hair; and the cysteine-rich pigment pheomelanin, found in red hair. 2. Melanocytes derive from the neural crest and migrate into the epidermis during em bryogenesis. Although they are scattered among the keratinocytes of the stratum basale, they are not attached to them by desmosomes. They have round cell bodies, central nuclei, and long cytoplasmic processes that pass between the cells of the strata basale and spinosum and terminate in small indentations on the keratinocyte surfaces. Melanocytes make up 10-25% of this layer's cells but do not participate in keratinization.
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