Anatomy and physiology of the perionychium.

Only primates have a perionychium on the dorsal distal portion of each finger and each toe. The flat nail on the end of the human finger allows for increased sensory perception in the pad of the finger and for efficient and accurate picking up of small objects. It also serves as a guard to protect the very sensate fingertip, and functions as a temperature regulator. Nail loss or deformity can be not only an aesthetic but also a functional problem. This article details the anatomy and physiology of the perionychium, knowledge that is essential to providing optimum care for these specialized structures.