Final answer:
The eponychium, also known as the cuticle, is the extension of excess cuticle at the base of the nail, which meets the proximal end of the nail body and is part of the nail fold.
Step-by-step explanation:
The extension of excess cuticle at the base of the nail is known as the eponychium, also commonly referred to as the cuticle. The nail fold meets the proximal end of the nail body to form the eponychium. The nail root is the part of the nail that is lodged in the epidermis, from which the nail grows. The nail matrix is a deep layer of epidermal tissue at the proximal end of a nail where nail growth occurs. Together, these structures form a complex that is essential for the protection and function of the nail.