Nail root

the nail root is the proximal, hidden segment of the nail matrix, located beneath the proximal nail fold, and is the primary site of nail plate production and growth.

The nail root is the most proximal portion of the nail unit, anatomically referred to as the proximal nail matrix. It lies beneath the proximal nail fold and is not visible externally. The nail root is embedded in a pocket-like invagination that runs parallel to the skin surface, with the proximal nail fold forming the roof and the nail matrix forming the floor. The matrix epithelium of the nail root is responsible for generating the bulk of the nail plate, particularly its superficial third, while the distal matrix contributes to the deeper layers of the nail plate. The nail root is anchored to the underlying distal phalanx by specialized connective tissue, including the onychodermis, which contains nail-specific fibroblasts (onychofibroblasts) and serves as a counterpart to the follicular dermal papilla in hair follicles.

The lunula, the visible half-moon-shaped area at the base of the nail, represents the distal part of the matrix but is not synonymous with the nail root itself.