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What are the white semi-circles at the bottom of our finger and thumb nails? © Getty Images

What are the white semi-circles at the bottom of our finger and thumb nails?

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The aptly named lunula is the white crescent moon shape found at the bottom of the nails of your fingers and toes, but why do we have them?

Asked by: Calum Ball, Worthing

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Your fingernails and toenails are made from keratin protein that is secreted by a layer of living tissue at the base of the fingernail called the nail matrix. The crescent moon shape, or lunula, is the part of the matrix that pokes out from under the flesh of your finger.

In some people it barely protrudes and is only really visible on the thumb and big toe. The lunula looks white because the epidermis is thicker beneath the matrix and it blocks the pink colour from the blood vessels below.

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Authors

luis villazon
Luis VillazonQ&A expert

Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.

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