Why Is Skin Lighter on Hands?
Skin pigmentation is influenced in large part by a black/brown substance called melanin. Carotene, which is yellow, is another pigment that affects skin color--especially where skin is thick, such as the palms of the hands.
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Skin
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The skin, or epidermis, has four to five layers. From deep to superficial these layers are the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum and the stratum corneum. The stratum corneum is found only in thick skin, such as that which covers the soles of the feet and the palms of the hands.
Melanocytes
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Melanocytes are found in the stratum basale of the epidermis. They produce melanin in response to genetic factors and environmental factors, such as exposure to ultraviolet (UV) radiation.
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Melanin
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Melanin breaks off from melanocytes as small granules of pigment. The granules are absorbed by epidermal keratinocytes. These skin cells then localize the pigment granules such that they shield the cell's nucleus, protecting the DNA from UV radiation.
Carotene
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Carotene is a yellowish pigment found in vegetables and egg yolks. A diet rich in carotene results in the accumulation of yellow pigment in the stratum corneum, where skin is thickest. Corns and calluses tend to be yellow in color.
Fun Fact
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Dark-skinned people and light-skinned people have the same number of melanocytes, but dark-skinned people produce larger quantities of melanin. Additionally, the melanin produced in light-skinned people tends to degrade more rapidly than it does in dark-skinned people.
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References
Resources
- Photo Credit hands in hands against sky, friendship concept image by JoLin from Fotolia.com
