What is the term for the skin located underneath the free edge of the nail?

The term for the skin located underneath the free edge of the nail is the hyponychium. This structure serves as a protective barrier, helping to prevent pathogens and debris from entering the nail bed. The hyponychium is critical for nail health as it aids in securing the nail plate to the underlying skin. It creates a seal that keeps moisture in and pathogens out, contributing to the overall integrity of the nail unit.

The matrix, on the other hand, is the tissue located under the base of the nail, which is responsible for nail growth. The cuticle refers to the layer of dead skin cells that protects the area where the nail grows from the nail bed. The lunula is the visible part of the matrix at the base of the nail, often recognized as the white crescent shape. Each of these other terms refers to different parts of the nail anatomy and their functions, but none define the skin beneath the free edge as accurately as the hyponychium does.