Answer :
Final answer:
When skin is exposed to sunlight, melanocytes in the epidermis produce melanin, a pigment that protects DNA from UV ray damage and balances vitamin D production. The sun's UV rays stimulate more melanin production, causing the skin to darken or tan. It's essential to note that significant and repeated UV exposure may increase skin cancer risk.
Explanation:
When skin is exposed to sunlight, the melanocytes in the stratum basale of the epidermis are stimulated. These cells contain small organelles called melanosomes that create, store, and transport melanin.
The type of melanin produced can be eumelanin, which is black or brown, or pheomelanin, which gives a red color. Dark-skinned individuals produce more melanin than those with lighter skin.
The sun's UV rays trigger the production of melanin in keratinocytes, inducing a tan.
The accumulation of melanin has the crucial role of protecting the DNA of epidermal cells from UV ray damage and preventing the breakdown of folic acid, a vital nutrient. However, excessive melanin can interfere with vitamin D production, necessary for calcium absorption, which tells us that the level of melanin in our skin is a balance between sunlight/folic acid and protection from UV radiation/vitamin D production.
UV light can stimulate responses such as tanning, which is a defense mechanism where the body produces pigments to absorb future exposures in inert skin layers, protecting our living cells from UV damage. Exposure to UV light also spurs the production of vitamin D.
It's also important to note that extended and repeated exposure to UV, particularly UV-B and UV-C wavelengths, can cause sunburn and increase the risk of skin cancer.
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