The Probert Encyclopaedia of Medicine

NAILS

In humans the nails are flattened, horny, protective coverings on the upper surface of the outer segments of the fingers and toes comprised of dead cells containing the fibrous protein keratin. Each nail consists of a root concealed within a fold of the skin; an exposed body attached to the surface of the skin; and a free anterior extremity called the edge. The skin below the root and body of the nail is termed the matrix. The matrix is thick and covered with highly vascular papillae, and its colour is seen through the transparent horny tissue. Near the root the papillae are smaller and less vascular making this portion of the nail appear whiter. From its crescent form this portion is termed the lunula or moon. The nail advances forward by the successive growth of new cells at the root and under the body of the nail. Homologous structures in other animals include the hooves of horses and the claws of birds.
Research Nails