The human skin color is primarily due to melanin, it ranges from skin almost black in appearance to white with a pinkish tinge due to blood vessels underneath. Variations in skin hue are mainly of genetic origin and are associated with sunlight, but the evolutionary causes are not completely certain. The leading explanation is they are adaptations to sunlight intensities which produce vitamin D deficiency or ultra violet light damage to folic acid. Other hypothesis includes protection from ambient temperature, infections in the food and sexual selection. According to scientific studies, natural human skin color diversity is highest in black or sub-Saharan African populations.
In human, melanin is the primary determinant of skin color. It is also found hair, the pigmented tissue underlying the iris or the eye and the stria vascularis of the inner ear. In the brain, tissues with melanin include the medulla and zona rticularis of the adrenal glands and pigment bearing neurons within areas of the brain stem, such as the locus coeruleus and the substantia nigra
The melanin in the skin is produced by melanocytes, which are found in the basal layer of the epidermis. Although human beings generally possess a similar concentration of melanoctytes their skin, the melanocytes in some individuals and ethic groups more frequently or less frequently express the melanin- producing genes, thereby conferring a greater or lesser concentration of skin melanin. Some individual animals and humans have very little or no melanin in their bodies a condition known as albinism
Because melanin is an aggregate of smaller compound molecules, there are number of different types of melanin with differing proportions and bonding, pattern of these component molecules. Both pheomelanin and hair, but eumelanin is the most abundant melanin in humans as well as the form most likely to be deficient in albinism.
Keratin is one of a family or fibrous structural protein. Keratin is the protein that protects epithelial cells from damage or stress that has potential to kill the cell. It is the key structural materials making up the outer layer of human skin. It is the key structural component of hair and nails, and it provides the necessary strength and toughness for masticating organs, such as the tongue and the hard palate. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong unmineralized tissue found in reptiles, birds, amphibians and mammals. The only other biological matter know to approximate the toughness of keratinized tissue is chitin.
Keratinocytes in the cornified layer of the epidermis, these are proteins which have undergone keratinization. In addition, keratin filament are present in epithelial cells in general for example, mouse thymic epithelial cells know to react with antibodies for keratin 5, keratin 8 and keratin 4. These antibodies are used as fluorescent makers to distinguish subset of TECS in genetic studies of the thymus.
Keratin (also described as cytokeratined are polymers of types III and type IV intermediate filaments, which have only been found in the genomes of chordate (vertebrate, amphioxus, urochordate) nematodes and many other non-chordate animals seem to only have type VI intermediate filaments, iamins, which here a long rod domain (Vs a short rod domain for the keratins
There are four (4) pigments in the normal skin that affect its color. Melanin oxygenated hemoglobin reduced hemoglobin and various carotene of this melanin is the most powerful. The cells that produce it are the same in all races but there is wide variation in the amount produced and wide variation in the color, which ranges from black to light tan every adult, has about 60.000 melanin producing cells in each square inch of skin. Melanin cells also affect eye color when the cells are deep in the eye the is brown. An albino a person with no melanin has eyes that appear pink because the stronger pigment tat ordinarily masks the blood vessels is lacking.
The pigment that gives blood its color called hemoglobin has the next greatest effect on skin color. When it is combined with oxygen, a bright red is the result and this in tore produce the rosy complexion associated with good health in light skinned people. When such people suffer from reduced hemoglobin because of anemia, they appear to be excessively pale. A concentration of reduced hemoglobin gives the skin a bluish appearance because hemoglobin has a weaker coloring effect that the melanin that determines basic skin color, these variations are more visible in lighter-skinned individuals
The weakest pigment in the skin is the carotenes. These produce a yellowish tone that is increases by eating excessive amounts of carrots and orange. In people with black or brown skin, excess carotene is usually
Both collagen and melanin play a protective role in healthy skin. Melanin absorbs harmful ultra violet light and protects the skin from photo damage. Skin collagen molecules, thus creating the skin organ. It provides protection against disease and injury. The thicker the skin and the more melanin, the better the protective barriers against the effects of aging
Melanin is a class of biological pigments as photo-protection of skin. Pigment cells named melanocytes produce melanin in outer skin layer. All melanocytes produce melanin, but cells in darker skinned people produce more per cell. The two melanin produced by human skin include black- brown, eumelanin and yellow –red pheomelanin. Each melanin has seprate biological properties. Also women produce 3 to 4 percent less melanin in their skin than men.
Before global migration most humans with the darken skin lived closest to the equator. Melanin absorbs ultra violet light. Thus protecting humans from harmful radiation damage skin cells and promote melanoma cancere of the skin European Americans have a lot times higher risk of melanoma than African American even though melanin is protective complete shielding would be harmful because short wave uv radiation needs vitamins D is synthesized in the skin.