Nails are composed of a substance called keratin, a horny material which protects and wears. They are modified reptilian scales consisting of a hard top plate, the unguis, and a softer under plate, the subunguis. The subunguis corresponds to the bottom (ventral) side of a claw. In nails, this region is much reduced.
The crescent or whitish half-moon on the nail base, lies over an area called the matrix. Nails grow Trom the matrix, which is formed by the deepest layer of the outer epidermis, the germinative layer. Growth from the matrix is continuous unless it becomes seriously injured. The average nail grows about one-eighth of an inch a month. A fold of thin skin called cuticle surrounds the nail base.
Labels: human body