Answer
Nails are hard accessory skin structures that are located at the distal ends of the digits (fingers and ties). They are composed mainly of dead keratinized cells. The hard visible part of the nail is the nail plate. It comprises the free edge, the nail body, and the nail root:
The free edge is the part of the nail plate that overhangs the distal end of a digit; the body (nail body) is the major visible part of the nail that is firmly attached to underlying epidermis of the back of the end of digits; the root of the nail is the proximal end of the nail; it is covered by overlying skin.
Other structures associated with nails are the lunule, the nail fold, the nail groove, the nail bed, and the nail matrix:
The lunule is the opaque whitish-pinkish crescent-shaped part of the nail plate near the proximal end of the nail. The nail fold is a thin fold of tissue that surrounds the nail plate on three sides; the nail groove is a narrow depression that separates the margin of the nail plate from the nail fold; the nail bed is the skin under the nail plate,
A continuos layer of cutaneous epithelium begins as the cuticle-- a zone of dead cells-- that overhands the nail plate at its proximal end; this epithelium continues under the nail plate and ends as the hyponichium a the distal end of the digit. The hyponichium binds the the nail plate to the distal end of the finger.
There is also a nail structure called the cuticle. this is often confused with the eponichium.; the latter is the living finger tissue at the proximal end of the nail. The cuticle is dead tissue that binds the eponichium to the nail plate and extendds around the distal lateral borders of the nail plate.
Finally there is the nail matrix: this is a thickened area of the stratum basale of the epidermis at the proximal end of the nail plate. The nail grows by mitosis of the cells of the matrix.
Work Step by Step
The usual growth rate of finger nails is about 0.8-1.0 mm per week. This rate varies from person to person and with conditions of sex, diet, and physical activity. Toe nails grow slower than fingernails and in general, the rates of nail growth decrease with increasing age .
