The term “melanin” comes from the Greek word “melas,” which translates to dark or black. This term can be used to describe natural pigments that can be found in various organisms. Through melanogenesis, melanin is produced by special cells known as melanocytes.
In humans, melanogenesis occurs when there is exposure to ultraviolet radiation, resulting in darkened skin. Since melanin absorbs light effectively, this pigment helps dissipate more than 99.9% of the absorbed ultraviolet radiation. Because of this ability, it is believed that melanin helps to protect the skin cells from ultraviolet radiation damage. This decreases the risk of dermal degradation and folate depletion, both of which are considered to increase the risk of malignant melanoma or skin cancer. This finding was further correlated by the lower incidence of skin cancer among individuals with a higher concentration of melanin.
1. Melanin in Humans
Melanin is the main determining factor of skin color in humans. Not only is it found in skin, it is also found in hair, the stria vascularis located in the inner ear, and the pigmented tissue underneath the iris of the eye. It can even be found in the brain where tissues with melanin include pigment-bearing neurons (such as substantia nigra and locus coeruleus) and medulla. In the adrenal gland, it can also be found in the zona reticularis. In the skin, the melanocytes in the basal layer of the epidermis produce melanin. However, in most cases, humans possess similar concentrations of melanocytes in the skin but these cells produce variable amounts of melanin. There are some humans who have very little to no melanin. This condition is known as albinism.