Melanin is a natural pigment produced by the human body. It is the substance that actually gives skin and hair its color, as well as the eyes. It provides color to other animal parts such as scales or feathers. The amount of melanin in the skin affects its tone, with dark skin people having a large amount and those with low melanin having light skin.
Humans and many species of animals have a special type of cells in the skin, named melanocytes. These dedicated cells produce the melanin pigment, as a secondary product in synthetizing tyrosine, an amino acid. Because of this, melanin is sometimes considered to be a chemical compound.
Melanin has two main types but its actual color is influenced by genetic factors. It can be anywhere from yellow to dark brown, including red. The most common type is brown and known as eumelanin. The second is between red and brown and is named pheomelanin, which is usually found in people with red hair and freckles. The actual color and amount of melanin in every person’s skin depends on a number of factors.
When the skin is exposed to sunlight or other sources of UV radiation, it produces melanin as a form of protection, in order to preserve its DNA integrity. The more a person is exposed to the sun, the more pigment will be produced in the skin to create a barrier.
The amount of melanin is also influenced by genetic inheritance. Some races have adapted to long periods of warm weather and sun exposure, and already start with a dark skin color. Skin tone is actually the most important aspect that determines human ethnicity and race. Even if considered controversial today, skin color is an obvious trait that differentiates people and makes each one unique.
All people have around the same total number of melanocytes but some of them are larger than others. Bigger cells are able to produce more pigment than normal ones.
There are also a number of diseases that influence the production of melanin. Vitiligo is a skin condition that causes the death of melanocytes, which eliminates melanin from the skin. Albinism is a genetic issue that prevents any pigment production at all. It is only one of the conditions associated with the lack of melanin, but probably the most well-known. It is not restricted to humans, since animals can suffer from albinism and even plants can lack this essential pigment.
There are a number of varieties of albinism. It usually affects the skin, which lacks its natural pigment, but the hair or the eyes can be targeted as well. When the eyes don’t have the normal amount of melanin, vision is also harmed in most cases. The lack of melanin has many dangerous effects and it usually causes a lower life expectancy.
All of these factors are important and influence the final level of skin melanin. Depending on each particular case, one or more of these factors can be more significant than others.
Besides its obvious cosmetic effect, melanin plays many key roles in the human body. The best known is the protection from harmful UV radiation found in sunlight, which would otherwise have devastating effects. It doesn’t stop all UV radiation, although if the protection it offers is enough in most situations, even people with very dark skin can be sunburn.
However, the protection provided by melanin is quite effective. People with dark skin have enough pigment in their skin to stay for several hours in the sun and avoid sunburn. Just a few minutes of direct sun exposure are enough to burn the skin of a person with a lighter tone. Low amounts of melanin are the direct cause of many diseases, such as eye cataract. The most dangerous risk is the one of skin cancer, a potentially lethal disease.
Besides providing UV protection, melanin is also able to store and absorb the heat generated by sunlight. This effect is critical for animals with cold blood, who rely on the sun for heating. Many species depend on sunlight and other outside sources of heat in order to regulate their body temperature. These include lizards, snakes, fish and many others.
The human body also uses this effect of melanin in the eyes. The pigment is able to reduce the amount of light that is allowed to enter the eyes and absorbs any excess rays. It is a very important process that increases visual accuracy.
What is the work structure of melanin?
Melanin is produced in the basal layer of the skin, which is the bottom part of the epidermis, the layer found on the skin’s exterior. The synthesis happens in this basal layer in special cells named melanocytes. During a process known as melanogeneis, packets of pigment named melanosomes are produced. Melanocytes are stimulated by the action of sunlight, after harmful UV radiation starts to attack cell nuclei in the skin. Dendrites, which are projections shaped like tentacles, carry the packets of melanin to skin cells named keratinocytes. These tentacle-like structures insert the pigment into the skin cells. As soon as the melanosomes are inside a cell, the melanin spreads in order to shield the nucleus from ultraviolet radiation. The main goal is to prevent the mutation of the DNA material found in the organelle. These special skin cells migrate to the top of the skin, in order to protect the ones located deeper. After a while, they die and fall off.
Types of melanin
Melanin actually consists of several different types, the most important are neuromelanin, eumelanin and pheomelanin. The first type, eumelanin, is part of most parts of the body, including the skin, hair and other dark areas, such as the areolas around nipples. The color of this pigment is either brown or black and can be found in large amounts in the skin and hair of blacks and other people with dark tones. A lack of this pigment in the hair causes it to be blonde. The role of eumelanin is protection from UV rays, since people with dark skin live in hot climates and spend a lot of time in the open. These pigments are also known as photo-protectants due to their ability to reduce the effect of harmful sunlight.
The second type of pigment is also found in the skin and hair and named pheomelanin. People with red hair have large amounts of this compound, which has a red or pink color. It is less effective against sun rays when compared with eumelanin and fails to provide the same degree of protection. It is sensitive to light and its ability to absorb radiation is low, which makes red-haired people vulnerable to skin cancer. This pigment is also a lot more common in the skin of females. Pheomelanin makes the skin very sensitive to the sun, a problem that only gets worse with aging.
Neuromelanin is a special variety of melanin that is present in the eyes and inside the brain. It plays a vital role in the body and a lack of it will cause very serious neurological diseases. However, scientists have failed so far to fully understand the functions of this pigment. It is found in the structure of the human eye, making it opaque to light and absorbing excess radiation. Without a proper amount of neuromelanin during youth, the retina will not develop well. It doesn’t seem to have any effect on the normal growth of other parts of the eye.