At the mention of the word melanin, our minds promptly tune to people who have black skin. We imagine it as a substance that makes black people’s skin drip with honey. These are only one of our thoughts but what happens in reality? Have you wondered about those that have lighter skin? Do such individuals have melanin at all?
In this article, we wander on a journey to discover more about melanin and its significance in our human lives.
Melanin is a natural pigment responsible for the colour of our skin, hair and eye colour. The type and amount of melanin produced leads to variations present.
The colour of a person's skin is decided mainly by genetic factors however, external factors will affect it. The genetic factor responsible for skin colour is melanin whereas the external factor is principally thanks to exposure to sunlight.
Genetic factors - Melanin
There are two main types of melanin
1. Eumelanin 2. Pheomelanin
Eumelanin is responsible for providing brown and dark hues. Hence, this kind of melanin is found mostly in black people and all the shades of brown. Melanin is an inherited feature that is transferred from parents to offspring. It means that one is probably going to become fair if born to light-skinned parents and dark when born to dark-skinned couples.
The skin colouring depends on the type and amount of eumelanin a person possess. The different shades of black are a result of the varying amount of melanin present. A person can have both the brown and black hue found in eumelanin. This is because the gene responsible for eumelanin is polygenic. This means that there are different genes responsible for providing identical dark and brown hues, thus variations will exist. Blonde individuals have a touch of brown hue and no black form of eumelanin whilst albinos have little to zero of any of the hues found in eumelanin.
Pheomelanin is responsible for providing red and yellow hues. Pheomelanin is responsible for the pinkish parts of the body such as the lips and the nipples. Thus, the deeper the colour, the higher the amount of pheomelanin present.
External factors- UV light from sunlight
It has been asserted that melanin is produced more when an individual is exposed to sunlight. It may be evident as people always complain of becoming dark after passing through the sun for a protracted period. The type of melanin produced is eumelanin. Our body produces it to shield us from harmful radiations from the skin which can cause injury and disorders to the skin.
Layers of the skin
The skin is made up of the epidermis and dermis. The epidermis is the region where it all goes down. The epidermis is made up of cells called keratinocytes and melanocytes. Keratinocytes form the outer layer of the epidermis whilst the melanocytes form the inner part of the epidermis. Melanin is produced by star-shaped melanocytes. Their production is triggered by exposure to sunlight. Other factors that may trigger its production are hormonal imbalances, ageing and inflammation processes.
Melanocytes produce eumelanin depending on the genetic characteristic of the individual. The melanin produced then travel to the outer cells - keratinocytes where they form a clump around the nucleus.
The nucleus is responsible for cell activity because they contain the genes, hence, if harmful radiations get thereto, it would cause mutations and result in disorders and cancers. Thus, the melanin produced is the body's mechanism of protecting itself.
Therefore, the longer a person spends within the sun, the greater the production of eumelanin to protect the cells of our skin and therefore the darker an individual appears.
This also explains why people who live far from the equator have light skin. Scientists believe that, a long time ago, all humans used to be dark because they all resided in Sub-Saharan Africa which is close to the equator. As time went on, people moved away from the equator to occupy other parts of the world. The lack of exposure to the sun gradually reduced the production of eumelanin which was then transferred to their offspring and resulted in lower production of dark and brown hues.
As stated above, melanin is responsible for the colour of our hairs. Eumelanin will give rise to people with either black or brown hair and all the different shades in between. Blondes have a little brown hue from eumelanin and no black hue. Albinos have little to zero eumelanin.
Pheomelanin is found in higher quantities in blondes. It gives them the red to orange hair colours.
Hair colour can be changed either permanently or temporarily with chemicals. During permanent hair colouring, the natural pigment is removed permanently from the hair cuticle and replaced by synthetic chemicals like bleach.
Semi-permanent colours which are temporary are applied to colour the hair during a shampoo or hair wash. They can be removed after a while because they do not affect the root of the hair. It must be noted that both types are found in all humans but the ratio differs.
The colour of a person’s eye is influenced by the pigmentation of a structure called the iris, which surrounds the pupil and helps control how much light can enter the eye. The colours range from very light blue to dark brown. This range depends on the quantity and type of melanin being produced. Melanin is polygenic(different genes are responsible for the production of the pigment) hence, variations will result.
People with brown eyes have a higher quantity of eumelanin whilst people with blue eyes have less of this type. Usually, an individual will have eyes with the same colour on both sides but this is not always the case. Some individuals have different colours on each side of their eyes, a condition termed Heterochromia. This happens as a result of injury, mutation and even genetics.
Eye colour is influenced by our genes but similar to the rest of the human body, humans have found ways to manipulate the physical appearance. Coloured contacts are a choice to temporarily change the iris colour.
It may be true that the skin glows when hit by sunlight but the next time you hear of melanin, think about the hair and eyes too and don't forget to give credits to melanin for it is the accountable source.
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