Melanin is a special pigment that gives the skin and hair its natural color. It also gives color to the iris of the eye, feathers and scales. It makes the skin tanned, but also produces unwanted freckles, birthmarks and other colored marks on the body.
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Mysterious melanin is an amorphous suspension of polymeric compounds that colors tissues of animals, plants, mushrooms and even microorganisms. Melanin can be black, yellow and brown in color. These melanin types determine the dark color of beans and grape pits, make banana peels brown, color insect wings in different shades; give their special colors to shelf fungus and black truffle.
In addition to melanin the skin color is also determined by reduced hemoglobin that gives the skin blue and even cyanotic color; by oxygenated hemoglobin that gives the skin reddish color and by carotinoids that make the skin colored peach.
With humans and other vertebrates melanin forms in special sea-star shaped cells called melanocytes in the basal layer of epidermis and then transforms into granules where pigments are combined with protein. Melanocytes inject melanin grains into the cells of the upper skin layer (cortical layer of the hair and the iris of the eye) and determine their color.
Melanin is formed as part of the process of metabolizing an amino acid called tyrosine under the influence of special ferment tyrosinase. However, some researchers are sure that melanin can be formed independently of ferments. As a result of the metabolizing process the amino acid dioxyphenylalanine is first formed, then dioxyphenylalanine molecules also oxidize and the transformations produce melanin. The entire of the process is regulated with special hypophysis hormones.
Melanin forms in the skin basically when it is exposed to the sun; and its basic function is to protect tissues from dangerous UV rays. So, tan on the skin is in fact a natural screen against hard radiation. And it is quite natural that people living in countries when the sun is particularly active have darker skin types. Europeans with light skin types have just sporadic melanin granules in epidermis while natives in Africa or Australia have their epidermis absolutely filled up with melanin granules. Black-skinned people have even lips colored dark as they have melanin in the mucous membrane while light-skinned people have no pigment in the mucous membrane at all.
The color of hair is determined by the amount of melanin in the cortical layer. Dark hair has a lot of pigment while fair hair has fewer granules that are of smaller size. Diffusive or non-granulated melanin makes the hair red.
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