Human skin colorHuman skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigmentation, which is the result of genetics (inherited from one's biological parents and or individual gene alleles), exposure to the sun, natural and sexual selection, or all of these. Differences across populations evolved through natural selection or sexual selection, because of social norms and differences in environment, as well as regulations of the biochemical effects of ultraviolet radiation penetrating the skin.
Human hair colorHuman hair color is the pigmentation of human hair follicles due to two types of melanin: eumelanin and pheomelanin. Generally, if more melanin is present, the color of the hair is darker; if less melanin is present, the hair is lighter. The tone of the hair is dependent on the ratio of black or brown eumelanin to yellow or red pheomelanin. Levels of melanin can vary over time causing a person's hair color to change, and it is possible to have hair follicles of more than one color on the same person.
MelanocyteMelanocytes are melanin-producing neural crest-derived 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, vaginal epithelium, meninges, bones, and heart. Melanin is a dark pigment primarily responsible for skin color. Once synthesized, melanin is contained in special organelles called melanosomes which can be transported to nearby keratinocytes to induce pigmentation. Thus darker skin tones have more melanosomes present than lighter skin tones.
MelanomaMelanoma, also redundantly known as malignant melanoma, is a type of cancer that develops from the pigment-producing cells known as melanocytes. Melanomas typically occur in the skin, but may rarely occur in the mouth, intestines, or eye (uveal melanoma). In women, they most commonly occur on the legs, while in men, they most commonly occur on the back. About 25% of melanomas develop from moles. Changes in a mole that can indicate melanoma include an increase in size, irregular edges, change in color, itchiness, or skin breakdown.
MelanosomeA melanosome is an organelle found in animal cells and is the site for synthesis, storage and transport of melanin, the most common light-absorbing pigment found in the animal kingdom. Melanosomes are responsible for color and photoprotection in animal cells and tissues. Melanosomes are synthesised in the skin in melanocyte cells, as well as the eye in choroidal melanocytes and retinal pigment epithelial (RPE) cells. In lower vertebrates, they are found in melanophores or chromatophores.
PigmentA pigment is a colored substance that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compounds. Pigments of prehistoric and historic value include ochre, charcoal, and lapis lazuli. In 2006, around 7.4 million tons of inorganic, organic, and special pigments were marketed worldwide. According to an April 2018 report by Bloomberg Businessweek, the estimated value of the pigment industry globally is $30 billion.
MelaninMelanin (ˈmɛlənɪn; ) is a broad term for a group of natural pigments found in most organisms. The melanin pigments are produced in a specialized group of cells known as melanocytes. There are five basic types of melanin: eumelanin, pheomelanin, neuromelanin, allomelanin and pyomelanin. The most common type is eumelanin, of which there are two types — brown eumelanin and black eumelanin. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino acid tyrosine is followed by polymerization.
TyrosinaseTyrosinase is an oxidase that is the rate-limiting enzyme for controlling the production of melanin. The enzyme is mainly involved in two distinct reactions of melanin synthesis otherwise known as the Raper Mason pathway. Firstly, the hydroxylation of a monophenol and secondly, the conversion of an o-diphenol to the corresponding o-quinone. o-Quinone undergoes several reactions to eventually form melanin. Tyrosinase is a copper-containing enzyme present in plant and animal tissues that catalyzes the production of melanin and other pigments from tyrosine by oxidation.
AlbinismAlbinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and reddish pink or blue eyes. Individuals with the condition are referred to as albinos. Varied use and interpretation of the terms mean that written reports of albinistic animals can be difficult to verify. Albinism can reduce the survivability of an animal; for example, it has been suggested that albino alligators have an average survival span of only 24 hours due to the lack of protection from UV radiation and their lack of camouflage to avoid predators.
Human skinThe human skin is the outer covering of the body and is the largest organ of the integumentary system. The skin has up to seven layers of ectodermal tissue guarding muscles, bones, ligaments and internal organs. Human skin is similar to most of the other mammals' skin, and it is very similar to pig skin. Though nearly all human skin is covered with hair follicles, it can appear hairless. There are two general types of skin, hairy and glabrous skin (hairless). The adjective cutaneous literally means "of the skin" (from Latin cutis, skin).
