The nail organ is an integral component of the digital tip. It is a highly versatile tool that protects the fingertip, contributes to tactile sensation by acting as a counterforce to the fingertip pad, and aids in peripheral thermoregulation via glomus bodies in the nail bed and matrix.
Because of its form and functionality, abnormalities of the nail unit result in functional and cosmetic issues. The structures that define and produce the nail (nail plate) include the matrix (sterile and germinal), the proximal nail fold, the eponychium, the paronychium, and the hyponychium (see the images below). Collectively, the nail bed (sterile matrix), nail fold, eponychium, paronychium, and hyponychium are referred to as the perionychium.
Nail surface anatomy.
See 15 Fingernail Abnormalities: Nail the Diagnosis, a Critical Images slideshow, to help identify conditions associated with various nail abnormalities.