The stratum corneum, or horny layer, of the epidermis gives rise to fingernails and toenails. Like this outer layer, nails are composed primarily of the tough protein keratin.
Nails have three main parts: the nail plate, the nail bed, and the nail matrix. The nail plate is the hard part of the nail, composed of layers of dead cells. The nail bed sits beneath the nail plate. Like skin elsewhere in the body, the nail bed is skin with a layer of epidermis and a layer of dermis. The epidermis of the nail bed is attached to the nail plate via grooves called matrix crests. This epidermis of the nail bed moves toward the end of the nail as the nail grows. The portion of the nail bed that sits at the base of the nail plate is called the nail matrix. The nail matrix contains nerves and blood vessels, and it gives rise to nail plate cells at the root of the nail.
As the nail grows, new nail plate cells in the nail root push older cells up the nail plate. As they are pushed up the nail plate, these cells become flattened and translucent. A small portion of the nail matrix is visible as a white crescent at the base of some nails. This is called the lunula, or small moon. The cuticle is a protective layer of dead cells that cover and seal the back of the nail plate. Finally, the hyponychium, or quick of the nail, sits between the open edge of the nail and the fingertip and protects the nail bed.Nails serve several functions. They help protect the delicate tips of fingers and toes from injury. They exert a counterpressure on the fingertip, which can help with precise movements and touch sensitivity. Finally, nails provide a valuable tool for cutting, scraping, or pinching very fine objects.