Final answer:
Nails are accessory organs of the skin located on the fingertips and toes, consisting mainly of keratin. Their functions include protection, sensation enhancement, and as tools. Nails grow from the matrix with new keratinocytes forming the hard nail plate.
Step-by-step explanation:
Nails: Structure and Function
Nails are accessory organs of the skin located at the distal ends of the fingers and toes. A nail is comprised of three main parts: the nail root, which is where the nail begins from a deep layer of the epidermis known as the nail matrix; the nail plate, which is the visible part of the nail; and the free margin, which is the part of the nail that extends beyond the end of the digit. These structures are supported by the nail bed and protected by the cuticle and nail fold.
The primary functions of nails include protecting the fingertips, enhancing tactile sensation by providing a counterforce when grasping objects, and acting as tools for various activities. The nails are composed mostly of dead keratinocytes, which contain the protein keratin, making them hard yet flexible. This composition is shared by the outermost surface of the skin and hair, which also primarily consist of keratin.
Nails grow from the nail matrix at the proximal end through the division of stem cells that give rise to keratinocytes. As new cells are formed, older cells are pushed out, causing the nail to extend over the finger or toe. Unlike hair growth, which can be perceptible daily, nails grow at a slower rate and cutting nails is painless since they consist of dead cells and lack nerve endings.