"in the brain, though its function remains obscure. In the human skin, melanogenesis is initiated by exposure to UV radiation, causing the skin to darken. Melanin is an effective absorbent of light; the pigment is able to dissipate over 99.9% of absorbed UV radiation. Because of this property, melanin is thought to protect skin cells from UVB radiation damage, reducing the risk of cancer, and it is considered that exposure to UV radiation is associated with increased risk of malignant melanoma, a cancer of melanocytes (melanin cells). Studies have shown a lower incidence for skin cancer in individuals with more"
"effects of tanning. Around the same age, women experience darkening of some areas of their skin. Human skin color fades with age. Humans over the age of thirty experience a decrease in melanin-producing cells by about 10% to 20% per decade as melanocyte stem cells gradually die. The skin of face and hands has about twice the amount of pigment cells as unexposed areas of the body, as chronic exposure to the sun continues to stimulate melanocytes. The blotchy appearance of skin color in the face and hands of older people is due to the uneven distribution of pigment cells"
"pigment melanin in the skin increases when exposed to moderate (depending on skin type) levels of radiation; this is commonly known as a sun tan. The purpose of melanin is to absorb UV radiation and dissipate the energy as harmless heat, protecting the skin against both direct and indirect DNA damage from the UV. UVA gives a quick tan that lasts for days by oxidizing melanin that was already present and triggers the release of the melanin from melanocytes. UVB yields a tan that takes roughly 2 days to develop because it stimulates the body to produce more melanin. Medical"
"Skin with little or no melanin is almost white. Other factors influence skin color in a lesser degree, including the amount of blood in blood vessels (because of the color of blood), skin thickness and content of carotenoids in skin. Melanin in synthesized in melanosomes which are organelles produced in melanocytes. Melanocytes are cells dedicated to this function that are present in the skin, hair follicles, and other structures of the body. The synthesis of melanin (also called ""melanogenesis"" and ""melanization"") involves a chain of enzyme-catalyzed chemical reactions and non-enzyme-catalyzed reactions. The main precursor to melanin is -tyrosine. The first"
"a chemical called alpha-melanocyte-stimulating hormone (α-MSH), which is produced by the body, from outside the cell. When MC1R comes into contact with α-MSH, a complex reaction is triggered inside the cell, and the melanocyte begins to produce black-brown pigment (eumelanin). Without the stimulation of α-MSH, the melanocyte produces red-yellow pigment (pheomelanin) by default. Various mutations in the human ""Mc1r"" gene result in red hair, blond hair, fair skin, and susceptibility to sundamaged skin and melanoma. Polymorphisms of ""Mc1r"" also lead to light or red coats in mice, cattle, and dogs, among others. The ""Extension"" locus was first suggested to have"
"Melanocyte Melanocytes 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. Functionally, melanin serves as protection against UV radiation. Melanocytes also have a role in the immune system. Through a process called melanogenesis, melanocytes produce melanin, which is a pigment found in the skin, eyes,"
"hair, nasal cavity, and inner ear. 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 increased melanogenesis. The purpose of melanogenesis is to protect the hypodermis, the layer under the skin, from damage by UV-B radiation. The color of the melanin is black, allowing it to absorb a majority of the UV-B light and block it from passing through the epidermis. Since the action"
"protect them from genetic damage. One melanocyte supplies melanin to thirty-six keratinocytes according to signals from the keratinocytes. They also regulate melanin production and replication of melanocytes. People have different skin colors mainly because their melanocytes produce different amount and kinds of melanin. The genetic mechanism behind human skin color is mainly regulated by the enzyme tyrosinase, which creates the color of the skin, eyes, and hair shades. Differences in skin color are also attributed to differences in size and distribution of melanosomes in the skin. Melanocytes produce two types of melanin. The most common form of biological melanin is"
"causing these cells to differentiate into melanocytes for the skin. Melanocyte Melanocytes 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. Functionally, melanin serves as protection against UV radiation. Melanocytes also have a role in the immune system. Through a process called melanogenesis, melanocytes produce"
"attractive a young woman is. Human skin color Human skin color ranges in variety from the darkest brown to the lightest hues. An individual's skin pigmentation is the result of genetics, being the product of both of the individual's biological parents' genetic makeup, and exposure to sun. In evolution, skin pigmentation in human beings evolved by a process of natural selection primarily to regulate the amount of ultraviolet radiation penetrating the skin, controlling its biochemical effects. The actual skin color of different humans is affected by many substances, although the single most important substance is the pigment melanin. Melanin is"
"in the core of each hair. Melanin is also responsible for the color of the skin and of the eyes. There are only two types of pigment: dark (eumelanin) or light (phaeomelanin). Combined in various combinations, these pigments create all natural hair colors. Melanin itself is the product of a specialized cell, the melanocyte, which is found in each hair follicle, from which the hair grows. As hair grows, the melanocyte injects melanin into the hair cells, which contain the protein keratin and which makes up our hair, skin, and nails. As long as the melanocytes continue injecting melanin into"
"color change is due to MSH stimulating the dispersion of melanin pigment in dermal (skin) melanophore cells. Pars intermedia Pars intermedia is the boundary between the anterior and posterior lobes of the pituitary. It contains three types of cells - basophils, chromophobes, and colloid-filled cysts. The cysts are the remainder of Rathke’s pouch. In human fetal life, this area produces melanocyte stimulating hormone or MSH which causes the release of melanin pigment in skin melanocytes (pigment cells). However, the pars intermedia is normally either very small or entirely absent in adulthood. In lower vertebrates (fish, amphibians) MSH from the pars"
"all; there may be blotchy, uneven areas, patches of brown to gray discoloration or freckling. Apart from blood-related conditions such as jaundice, carotenosis, or argyria, skin pigmentation disorders generally occur because the body produces either too much or too little melanin. Various types of albinism are a result of genetic mutations affecting different parts of the melanin production pathway. In a person with albinism, melanocytes can be entirely absent, or fail to produce melanin, or melanosomes can fail to mature and be transferred to keranocytes. The ability to produce melanin in patches around the body is a condition known as"
"is a compound found in plants, animals, and protists, and is derived from the amino acid tyrosine. Melanin is a photoprotectant, absorbing the DNA-damaging ultraviolet radiation of the sun. Vertebrates have melanin in their skin and hair, feathers, or scales. They also have two layers of pigmented tissue in the eye: the stroma, at the front of the iris, and the iris pigment epithelium, a thin but critical layer of pigmented cells at the back of the iris. Melanin is also present in the inner ear, and is important for the early development of the auditory system. Melanin is also"
"have darker skin pigmentation than their surrounding populations. Dark-skinned humans have high amount of melanin found in their skin. Melanin is derivative of the amino acid tyrosine. Eumelanin is the dominant form of melanin found in human skin. Eumelanin protects tissues and DNA from radiation damage of UV light. Melanin is produced in specialized cells called melanocytes, which are found at the lowest level of the epidermis. Melanin is produced inside small membrane-bound packages called melanosomes. People with naturally occurring dark skin have melanosomes which are clumped, large, and full of eumelanin. A four-fold difference in naturally occurring dark skin"
"skin melanocytes. In humans, the tyrosinase enzyme is encoded by the ""TYR"" gene. A mutation in the tyrosinase gene resulting in impaired tyrosinase production leads to type I oculocutaneous albinism, a hereditary disorder that affects one in every 20,000 people. Tyrosinase activity is very important. If uncontrolled during the synthesis of melanin, it results in increased melanin synthesis. Decreasing tyrosinase activity has been targeted for the betterment or prevention of conditions related to the hyperpigmentation of the skin, such as melasma and age spots. Several polyphenols, including flavonoids or stilbenoid, substrate analogues, free radical scavengers, and copper chelators, have been"
"design. Some of the most potent competitive reversible tyrosinase inhibitors are synthetic compounds with a potency hundreds of times that of kojic acid. Melanin is the main substance responsible for the color of the skin. Melanin is class of dark polymers generated by the body through the process of melanogenesis. Among the melanin pigmenting the skin and hair, two types can be distinguished based on its chemical composition and biological route of synthesis: the black/brown eumelanin and the red/yellow pheomelanin. The variation of skin color among individuals is mostly because of variation of the content of melanin in the skin."
"Human skin color Human skin color ranges in variety from the darkest brown to the lightest hues. An individual's skin pigmentation is the result of genetics, being the product of both of the individual's biological parents' genetic makeup, and exposure to sun. In evolution, skin pigmentation in human beings evolved by a process of natural selection primarily to regulate the amount of ultraviolet radiation penetrating the skin, controlling its biochemical effects. The actual skin color of different humans is affected by many substances, although the single most important substance is the pigment melanin. Melanin is produced within the skin in"
"melanins have their influence either alone or in conjunction, making either plain or multi-coloured coats. Sometimes, in a condition called agouti, they make multi-coloured individual hairs. The production of melanin occurs in melanocytes in a complex process involving the enzyme tyrosinase. Mammals have a gene that codes for the presence of tyrosinase in cells – called the TYR gene. If this gene is altered or damaged, melanin cannot be reliably produced and the mammal becomes an albino. Besides the TYR gene, several other genes can cause albinism. This is because other hormones and proteins are involved in melanin production, the"
"variation between different body parts is substantial), but organelles which contain pigments, called melanosomes, are smaller and less numerous in light-skinned humans. For people with very light skin, the skin gets most of its colour from the bluish-white connective tissue in the dermis and from the haemoglobin associated blood cells circulating in the capillaries of the dermis. The colour associated with the circulating haemoglobin become more obvious, especially in the face, when arterioles dilate and become tumefied with blood as a result of prolonged physical exercise or stimulation of the sympathetic nervous system (usually embarrassment or anger). Up to 50%"
"the liver. On lighter to medium skin tones, solar lentigenes emerge as small- to medium-sized brown patches of freckling that can grow and accumulate over time on areas of the body that receive the most unprotected sun exposure, such as the back of the hands, forearms, chest, and face. For those with darker skin colors, these discolorations can appear as patches or areas of ashen-gray skin. Melanin in the skin protects the body by absorbing solar radiation. In general, the more melanin there is in the skin the more solar radiation can be absorbed. Excessive solar radiation causes direct and"
"vitamin D from sunlight, which helps it absorb calcium. Females evolved to have lighter skin so their bodies absorb more calcium. The social significance of differences in skin color has varied across cultures and over time, as demonstrated with regard to social status and discrimination. Melanin is produced by cells called melanocytes in a process called melanogenesis. Melanin is made within small membrane–bound packages called melanosomes. As they become full of melanin, they move into the slender arms of melanocytes, from where they are transferred to the keratinocytes. Under normal conditions, melanosomes cover the upper part of the keratinocytes and"
"has mesodermal cells, pigmentation, such as melanin provided by melanocytes, which absorb some of the potentially dangerous ultraviolet radiation (UV) in sunlight. It also contains DNA repair enzymes that help reverse UV damage, such that people lacking the genes for these enzymes suffer high rates of skin cancer. One form predominantly produced by UV light, malignant melanoma, is particularly invasive, causing it to spread quickly, and can often be deadly. Human skin pigmentation varies among populations in a striking manner. This has led to the classification of people(s) on the basis of skin color. In terms of surface area, the"
"the dramatic mobilization of melanin upward in the epidermis and continues with the increased production of melanin. This accounts for the fact that dark-skinned people get visibly darker after one or two weeks of sun exposure, and then lose their colour after months when they stay out of the sun. Darkly pigmented people tend to exhibit less signs of aging in their skin than the lightly pigmented because their dark skin protects them from most photoaging. Skin colour is a polygenic trait, which means that several different genes are involved in determining a specific phenotype. Many genes work together in"
"that underlie the addiction. The term ""tanning"" has a cultural origin, arising from the color tan. Its origin lies in the Western culture of Europe when it became fashionable for young women to seek a less pale complexion (see Cultural history below). Melanin is a natural pigment produced by cells called melanocytes in a process called melanogenesis. Melanocytes produce two types of melanin: pheomelanin (red) and eumelanin (very dark brown). Melanin protects the body by absorbing ultraviolet radiation. Excessive UV radiation causes sunburn along with other direct and indirect DNA damage to the skin, and the body naturally combats and"
"iris, the cornea being transparent and the white sclera entirely outside the area of interest. Melanin is yellowish-brown to dark brown in the stromal pigment cells, and black in the iris pigment epithelium, which lies in a thin but very opaque layer across the back of the iris. Most human irises also show a condensation of the brownish stromal melanin in the thin anterior border layer, which by its position has an overt influence on the overall color. The degree of dispersion of the melanin, which is in subcellular bundles called melanosomes, has some influence on the observed color, but"
"exposure to UVB rays, melanocytes will produce melanin, a pigment that gives the skin its color tone. However, UVB will cause the formation of freckles and dark spots, both of which are symptoms of photoaging. With constant exposure to UVB rays, signs of photoaging might appear and precancerous lesions or skin cancer may develop. UVA rays are able to penetrate deeper into the skin as compared to UVB rays. Hence, in addition to the epidermal layer, the dermal layer will also be damaged. The dermis is the second major layer of the skin and it comprises collagen, elastin, and extrafibrillar"
"lowered life expectancy. Since both of these states are linked to the same mutated gene, large populations today are susceptible to sickle cell despite it being a fitness-impairing genetic disorder. the mutation of the TYR gene, also termed tyrosinase. This mutation causes the most common form of albinism. The mutation alters the production of melanin, thereby affecting melanin-related and other dependent traits throughout the organism. Melanin is a substance made by the body that is used to absorb light and provides coloration to the skin. Indications of albinism are the absence of color in an organism's eyes, hair, and skin,"
"skin responsible for protection from harmful UV radiation. When melanocytes are stimulated by solar radiation, melanin is produced. Melanin is one of the major absorbers of light in some biological tissue (although its contribution is smaller than other components). There are two types of melanin: eumelanin which is black-brown and pheomelanin which is red-yellow. The molar extinction coefficient spectra corresponding to both types are shown in Figure 3. Fat is one of the major components in tissue that can comprise 10-40% of tissue. Although not many mammalian fat spectra are available, Figure 4 shows an example extracted from pig fat."
"melanin pigmentations a defence-system in action. The microscope shows smoker's melanosis to be characterized by a melanin hyperpigmentation of the lower part of the oral epithelium, similar to sun-tanned skin. The hyperpigmentation consists of melanin granules which have the shape and colour of ""coffea beans"". They are produced by the dendritic, octopus-like melanocytes, seen between the epithelial cells situated closest to the epithelium/connective tissue border. In tobacco-users the melanocytes are stimulated to produce melanin granules and to distribute them out to the surrounding epithelial cells for further transport to the mucosal surface, like the mechanism in melanin-pigmented skin. Small amounts"
"by melanocytes, melanin-containing cells, that are usually located in the surface of the skin (the epidermis), but are in the deeper region (the dermis) in the location of the spot. Usually, as multiple spots or one large patch, it covers one or more of the lumbosacral area (lower back), the buttocks, sides, and shoulders. It results from the entrapment of melanocytes in the lower half to two-thirds of the dermis during their migration from the neural crest to the epidermis during embryonic development. Male and female infants are equally predisposed to Mongolian spot. People who are not aware of the"
"consumption by snails and isopods. Melanins are a family of dark-pigmented substances found in a wide range of organisms. Chemically they are closely related to dopamine, and there is a type of melanin, known as dopamine-melanin, that can be synthesized by oxidation of dopamine via the enzyme tyrosinase. The melanin that darkens human skin is not of this type: it is synthesized by a pathway that uses L-DOPA as a precursor but not dopamine. However, there is substantial evidence that the neuromelanin that gives a dark color to the brain's substantia nigra is at least in part dopamine-melanin. Dopamine-derived melanin"
"Melanin Melanin (; from ""melas"", ""black, dark"") is a broad term for a group of natural pigments found in most organisms. Melanin is produced by the oxidation of the amino acid tyrosine, followed by polymerization. The melanin pigments are produced in a specialized group of cells known as melanocytes. There are three basic types of melanin: eumelanin, pheomelanin, and neuromelanin. The most common type is eumelanin, of which there are two types—brown eumelanin and black eumelanin. Pheomelanin is a cysteine-derivative that contains polybenzothiazine portions that are largely responsible for the color of red hair, among other pigmentation. Neuromelanin is found"