Perionychium

The perionychium refers anatomically to the tissues that surround the nail unit, specifically including the lateral nail folds, the proximal nail fold, and the underlying nail bed and hyponychium. It encompasses all the soft tissue structures that border the nail plate on its sides and base, but does not include the nail plate itself.

The perionychium serves as a protective barrier for the nail matrix and bed, and is composed of specialized epidermal and dermal tissues with abundant vascular and neural supply. The lateral and proximal nail folds form a distally open frame for the growing nail, while the hyponychium acts as a barrier at the distal end of the nail unit, preventing pathogens and debris from entering the subungual space.