Answer :
Exposure to sunlight darkens the skin as a response to protect skin cells from harmful UV radiation. This process involves the production and build-up of melanin, a pigment that gives our skins its color, in the outer skin layers. The level of melanin in our skin is regulated by multiple factors, including the exposure to sunlight, ensuring balance between protection from UV damage and the production of vitamin D.
Exposure to sunlight can darken skin as an adaptive response by the body to protect its cells from harmful ultraviolet (UV) radiation. This process involves the production of melanin, a pigment produced by cells called melanocytes.
Melanin occurs in two primary forms: eumelanin (black and brown) and pheomelanin (red). UV rays stimulate keratinocytes, cells in the outer layer of the skin, to secrete chemicals that stimulate melanocytes. The subsequent accumulation of melanin in keratinocytes results in the darkening of the skin, which is often visible as a tan.
This increased melanin accumulation essentially functions as a natural sunscreen, protecting the DNA of epidermal cells from UV ray damage and preventing the breakdown of folic acid. However, an excess of melanin can disrupt the production of vitamin D, an important nutrient for calcium absorption. Thus, the melanin level in our skin is a fine balance governed by multiple factors including sunlight exposure, folic acid destruction, UV radiation protection, and vitamin D production.
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