Which portion of the living skin supports the nail plate as it grows toward the free edge?

The portion of the living skin that supports the nail plate as it grows toward the free edge is the nail bed. The nail bed is the soft tissue beneath the nail plate and provides the necessary support and cushion for the nail. This structure plays a critical role in the attachment of the nail plate, as it contains many blood vessels and nerves, which are essential for the nourishment and sensation of the nails.

When the nail grows, it moves forward over the nail bed, and the health of the nail bed is essential for the overall growth and appearance of the nail. The interaction between the nail plate and the nail bed is vital for maintaining the strength and integrity of the nails as they grow.

Other choices refer to different parts of the nail structure: the matrix is where new nail cells are generated, the hyponychium is the thickened layer of skin under the free edge of the nail, and the eponychium, or cuticle, covers the base of the nail plate. While these structures are important to nail anatomy, they do not provide the supporting function of the nail plate as it grows.