Normal, healthy nails grow in various shapes depending on the shape of what part?

The correct answer is based on the understanding of how nail growth is influenced by the underlying structures of the nail. The shape of the nails is primarily determined by the matrix, which is the tissue located under the base of the nail where new nail cells are produced. The matrix is responsible for the thickness, shape, and overall appearance of the nail as it grows. As new cells are generated in the matrix, they push older cells forward, ultimately forming the visible nail plate.

The other options address different aspects of nail anatomy but do not play a direct role in determining nail shape. For example, the fingers provide context for nail attachment but are not the origin of the nail structure itself. The eponychium, also known as the cuticle, serves to protect the matrix and does not influence the shape of the nail directly. The free edge is the part of the nail that extends beyond the fingertip and is shaped by the matrix but does not influence the growth process. Understanding the role of the matrix is essential for recognizing how nail growth and shape are established.