Final answer:
The shape of normal, healthy nails is determined by the shape of the nail matrix, which is the area where nail growth occurs and stem cells divide to form keratinocytes.
The correct answer is option B Matrix
Step-by-step explanation:
Normal, healthy nails can grow in a variety of shapes, depending on the shape of the nail matrix. The nail matrix is a deep layer of living epidermal tissue at the proximal end of the nail, where nail growth occurs. Stem cells in the nail matrix keep dividing to allow nail growth, forming the nail.
This area contains the necessary stem cells that divide to form keratinocytes, the cells that produce keratin, which make up the bulk of the nail. The shape and size of the nail matrix largely determine the width and thickness of the nail plate, influencing the final shape of the nail as it emerges from the epidermis.