Answer
Nails are hard because they are made up of tightly-packed, dead, keratinized cells. These cells are cemented together, and unlike the cells of the stratum corneum elsewhere, they do not shed.
Work Step by Step
The nail plate is formed of several layers of dead, keratinized cells. These cells derive from mitosis of epidermal cells of the matrix. The matrix is the area of the epidermis at the proximal end of the nail plate. Cell division in the matrix goes on at varying rates all through life. Newly formed cells push older cells forward:this process results in growth of the nails. . As cells move in direction of the nail edge and hyponichium, they become flatter, deposit more keratin and finally die. The nail plate is therefore mainly a structure created out of dead cells . It is very hard because the keratin fibers in these cells is formed from a specially tough high sulfur so-called alpha -keratin molecule
