A nail consists of the nail plate and the tissues which surround and underlie it. The nail plate has three parts; the matrix which is concealed within the skin; the fixed portion which adheres firmly to the nail-bed, and the free edge of the nail. The active growth area is the epidermis of the matrix, which underlies the skin of the nail-fold. Sealing off the potential space between the nail and the nail-fold is the cuticle, which has an important protective function. Under normal conditions, the nail plate is firmly attached to the nail-bed. (This may, however, change as a result of various disease processes.) The nail plate exhibits various colour tones ranging from white to pink, which are the result of reflected light from the tissue beneath the colourless nail. The whitish-grey colour of the free edge is due to the air underneath it. Nail is composed of hard keratin, the same protein from which hair is derived. Like hair, the nail plate has no nerves or blood supply, and is a ‘dead’ structure. Under natural conditions nails would extend indefinitely unless cut or worn away with use. Unlike hair growth, which is periodic, nail growth is continuous. The daily rate of extension is about one third of hair, or approximately 0-1 millimetre. It takes about 100 days for the fingernail of a healthy young person to be restored after removal.


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