• Núria Estapé, science journalist

    Whatai??i??s melanin for?

    16 May  Whatai??i??s melanin for?

    When we refer to the sun and to tanning, we refer to melanin. Melanin is produced when the sun touches the skin, making us go brown. This pigment darkens the skin to protect it from the damage caused by ultraviolet (UV) rays. Our hair and the iris of the eye also contain melanin. But what exactly is melanin and what is it for?

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    Melanin is not unique to humans, but is to be found in most living things. Thanks to melanin, some animals can change their colour as camouflage and plants have different colours. The melanin pigment is derived from tyrosine, an amino acid essential for our body to function properly. Melanin is made in the melanocytes (epidermal cells) and also in the hair follicles. Itai??i??s a bit like a coloured crayon, responsible for brownish and reddish tones in the skin and hair. But its main function is, in fact, to protect us against the damaging effects of UV radiation.

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    Light and colour

    Light is what enables melanin to do its work. Melanin production is stimulated by the UV light emitted by the sun. Melanin ai???neutralizes" these UV rays by absorbing them and then emitting them at different wavelengths to form colours visible to the human eye.

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    Substances like melanin that absorb light and then emit it as visible colours are called chromophores. One chromophore, for example, is responsible for the yellowish orange tint of the beta-carotene in carrots; another chromophore is chlorophyll, responsible for the different greens of plants.

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    In human skin there are two basic skin chromophores or dyes: haemoglobin, which colours the pinkish skins of the Caucasian or white races, and melanin, which is responsible for darker and black skin. Melanin also protects the iris of the eye. It also synchronizes with certain hormones to protect us from excessive solar radiation, or conversely, to ensure that our vital functions are maintained in the absence of light.

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    The melanin journey

    The melanocytes that make melanin have tentacles in contact with the keratinocytes, the most abundant cells in the surface of the epidermis. They pass the pigment particles stored in microscopic bags called melanosomes through these tentacles to the keratinocytes. From melanosomes melanin particles darken our skin.

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    The more melanosomes that reach the keratinocytes on the skin surface, the more the skin darkens. The inside of our forearms and legs is whiter than our face and neck because these areas have fewer melanocytes manufacturing melanin. Melanin accumulates in the areas of the skin where more sun protection is necessary; this happens, for example, with the areola of the nipple, which has a darker skin tone than the surrounding skin.

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    Eumelanin and pheomelanin

    In reality, our skin manufactures two types of melanin. People with fair skin and red hair produce more pheomelanin and brown and black people produce more eumelanin. Eumelanin absorbs most of the UV radiation, which is why it is considered a natural sunscreen. In other words, darkened pigmentation of the skin protects it.

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    Pheomelanin, in contrast, acts as a photosensitizer, making the skin more sensitive to sunlight; this is necessary, for example, to synthesize vitamin D. When we sunbathe, eumelanin darkens our skin; when we stop sunbathing, the proportion of pheomelanin increases and we gradually lose our tan.

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    When melanin fails to function

    Albinism is a genetic alteration that results in the absence of melanin. The characteristic appearance of the skin and hair of people with albinism reminds us that our hair ages and becomes grey or white due to a lack of melanin production.

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    Certain hormones also affect how this pigment functions. During pregnancy or menopause it is not unusual to suffer from pigmentation problems, such as vitiligo (loss of pigment in some areas of the skin) or melasma (excess pigmentation).

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    +info:

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    Mediterranean fair skin: a question of natural selection

    Skin bleaching: when skin has to be white buyclomidonlaine.com/buy-nolvadex-online/

    Redheads are more prone to melanoma

    More sun, more age spots

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