Nail anatomy

Abstract

The nail unit comprises the nail plate, the surrounding soft tissues, and their vasculature and innervation based upon the distal phalanx. The nail plate is a laminated keratinized structure lying on the nail matrix (15-25%), the nail bed with its distal onychodermal band (75-85%), and the hyponychium at its free edge. The distal part of the matrix, the lunula characterized by its half-moon shape, can be observed in some digits. The nail plate is embedded by the proximal and lateral folds. From the proximal nail fold, the cuticle (also known as the eponychium), adheres to the superficial surface of the proximal nail plate. The nail unit possesses a complex and abundant vascular network to ensure adequate blood supply. Finally, both the periungual soft tissues and the nail folds are innervated. The shapes, structure, and inter-relationships of these tissues are factors in the way nails present with disease and how we understand and manage those diseases. In particular, an understanding of the surgical anatomy is important for those undertaking diagnostic or curative operations on the nail. With this knowledge, the most appropriate surgery can be planned and the patient can be provided with accurate and clear guidance to enable informed consent.