A nail is a horn-like envelope covering the dorsal aspect of the terminal phalanges of fingers and toes in humans, most non-human primates, and a few other mammals. Nails are similar to claws in other animals. Fingernails and toenails are made of a tough protein called keratin, as are animals’ hooves and horns. The mammalian nail, claw, and hoof are all examples of unguis.
The nail consists of the nail plate, the nail matrix and the nail bed below it, and the grooves surrounding it.
The matrix is sometimes called the matrix unguis, keratogenous membrane, nail matrix, or onychostroma. It is the tissue (or germinal matrix) which the nail protects. It is the part of the nail bed that is beneath the nail and contains nerves, lymph and blood vessels. The matrix is responsible for producing cells that become the nail plate.
The width and thickness of the nail plate is determined by the size, length, and thickness of the matrix, while the shape of the fingertip itself shows if the nail plate is flat, arched or hooked. The matrix will continue to grow as long as it receives nutrition and remains in a healthy condition. As new nail plate cells are made, they push older nail plate cells forward; and in this way older cells become compressed, flat, and translucent. This makes the capillaries in the nail bed below visible, resulting in a pink color.