Which part of the nail covers the matrix?

The correct answer is the proximal nail fold. This structure plays a crucial role in the protection and formation of the nail. The proximal nail fold is the piece of skin located at the base of the nail, and it serves to cover the matrix, which is the area where new nail cells are generated.

The matrix is responsible for nail growth; as the cells mature, they harden and are pushed forward to form the visible part of the nail. The proximal nail fold provides a barrier that protects this sensitive area from potential damage and infection. Additionally, it helps create a seal that prevents moisture and debris from affecting the underlying matrix.

In contrast, the other options represent different parts of the nail anatomy but do not cover the matrix directly. The nail plate is the hard, visible portion of the nail; the lateral nail fold is the skin that runs along the sides of the nail; and the free edge is the part of the nail that extends beyond the fingertip. Understanding these distinctions is important for recognizing the protective and functional roles of each structure in nail health and growth.