Melanin is the pigment that controls our skin tone, our hair colour and the colour of our iris.
It can be found in various parts of the human body, including:
- Skin, where it affects skin tone
- The colour of our iris
• The vascular Groove in the inner ear
• Areas of the brain, the dark matter and the locus coeruleus
• The medulla and the reticular zona pellicuda of the adrenal gland
Melanin is produced by a group of specialised cells, called melanocytes. These are located in the lower layer of the epidermis and in the hair follicle matrix. These malanocytes produce granules called melanosomes. When these melanosomes are full of pigment, they are transferred to the neighbouring keranocytes. As part of the epidermal turn-over these adjoining cells migrate to the upper layers of the skin, taking their pigment with them. In this way the pigment gives our skin its characteristic colour.
Melanin is found in all people and forms complex compositions which cause the wide range of human skin colours.
We can find a wide range of Melanin types:
Eumelanins: this is dark Brown or black in colour, contains sulphur, and creates the darker colours. This is present in the areola, the skin and the grey hair colours (a small amount of eumelanin but without any other pigments), black, brown and fair hair, and is more common in black people. There are also black and brown eumelanin, and these are the second most common in young caucasions.
It is worth mentioning that when eumelanin is present in small quantities, the hair is usually fair.
Feomelanin: this is a yellow or reddish Brown pigments that has a higher sulphur content than those previously mentioned. This is responsible for the light colours. This type of melanin confers the pinkish and reddish colours and is the main melanin found in people with red/ginger hair. This type of melanin is not as protective against cancer caused by UV radiation as eumelanin.
Neuromelanin: is a form of melanin that is found in different area of the brain. The loss of this melanin may cause a range of neurological disorders.
Melanins provide the biological protection system against solar radiation. In order to do this, in the epithellial cells, the melanin granules are located in a supra-nuclear position giving maximum protection to the DNA against UV radiation. Getting a suntan means producing a greater quantity of melanin as the body protects itself against UV rays.
They also help with thermo-regulation which is necessary due to the absorption of solar radiation. Furthermore, they regulate the synthesis of Vitamin D. This vitamin is formed in the skin due to the action of UV radiation from exposure to the sun due to precursors located in the epidermis. As melanin absorbs UV radiation, it also controls the synthesis of Vitamin D. Thus, melanin protects the photo-sensitive metabolytes from degradation by solar radiation. It also has anti-radical properties.
Of interest: the albino condition is a genetic modification resulting in a lack of melanin. The characteristic appearance of the skin and hair of albinos brings to mind premature ageing. When hair turns grey or white, it is also due to a lack of melanin.
Certain hormones also intervene in the functioning of this pigment. During pregnancy or menopause problems of cutaneous pigment may occur, such as vitiligo (the loss of pigment in certain areas of the skin), or melisma (an excess of pigment in areas of the skin).