Answer :
Final answer:
Melanin is the skin darkening pigment that stains surrounding cells, causing them to darken. It occurs in two primary forms: eumelanin and pheomelanin. Darker skin produces more melanin.
Explanation:
Melanin is the skin darkening pigment that stains surrounding cells, causing them to darken. Melanin occurs in two primary forms: eumelanin (black and brown) and pheomelanin (red). Dark-skinned individuals produce more melanin than those with pale skin. Exposure to UV rays stimulates the production of melanin, which accumulates in keratinocytes and protects the DNA of epidermal cells from UV damage. However, excessive melanin production can interfere with vitamin D production.
Other medical conditions can also cause skin darkening. Liver disease or cancer can result in the accumulation of the yellow pigment bilirubin, causing the skin to appear yellow. Pituitary gland tumors and Addison's disease can lead to the release of excess melanocyte-stimulating hormone (MSH) and adrenocorticotropic hormone (ACTH) respectively, causing a darkening of the skin. Changes in oxygenation levels can affect skin color, resulting in ashen or blue appearance.
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