SKIN COLOR

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The color of the skin in the different races is due to pigmentation. The important pigment of the skin is melanin, of which there are many types widely distributed in the animal kingdom and range from yellow through brown to black in color.

In man, melanin occurs chiefly in the epidermis, and in the white race, in cells of the basal layer, where it tends to be disposed on the sunny side of the nuclei. Melanin occurs in the form of fine brown to black granules, but these commonly clump together if the pigment is abundant. The content of melanin in the epidermis is responsible for the difference in the color of the skins of the different races (black, brow, yellow and white). All have some melanin in their skins. An inherent inability in any individual of any race to produce melanin results in Albinism. Increased amount of melanin appear in the epidermis of white skin when it is exposed to ultraviolet light; this is called sun-tanning. The cells that synthesize melanin are melanocytes. The cell bodies of melanocytes are disposed either just beneath or between the cells of the basal layer of the epidermis. Before they make melanin, they appear in the basal layer as clear cells. The cell bodies of melanocytes in either position send out long processes which extend between or under epidermal cells; mostly the basalis and spinous layers. These processes end on epidermal cells. In due course, the melanin granules made by melanocytes, are taken into the cytoplasm of the epithelial cells reached by the long processes of the melanocytes.

By this means, the ordinary epithelial cells of the basal layer come to contain melanin pigments. It follows therefore that melanocytes cannot be distinguished from true epidermal cells by or because of their contained pigment. Histochemical test which pick out cells that have the functioning metabolic equipment required to make the pigment are used. This test is known as dopa test based on dopa reaction.

BONUS: The skin is the largest organ in the human body. That is as all around anatomy as it can get.