Melanocyte

Melanocytes (ⁱ/məˈlænəˌsaɪt, -noʊ-/ or /ˈmɛlənəˌsaɪt, -noʊ-/) are melanin-producing cells located in the bottom layer (the stratum basale) of the skin's epidermis, the middle layer of the eye (the uvea), the inner ear,meninges,bones, and heart. Melanin is the pigment primarily responsible for skin color. Once synthesised, melanin is contained in a special organelle called a melanosome and moved along arm-like structures called dendrites, so as to reach the keratinocytes.

Melanogenesis

Through a process called melanogenesis, these cells produce melanin, which is a pigment found in the skin, eyes, and hair. This melanogenesis leads to a long-lasting pigmentation, which is in contrast to the pigmentation that originates from oxidation of already-existing melanin.

There are both basal and activated levels of melanogenesis; in general, lighter-skinned people have low basal levels of melanogenesis. Exposure to UV-B radiation causes an increased melanogenesis. The purpose of the melanogenesis is to protect the hypodermis, the layer under the skin, from the UV-B light that can damage it (DNA photodamage). The color of the melanin is dark, allowing it to absorb a majority of the UV-B light and block it from passing through this skin layer.