Final answer:
The dead tissue that adheres to the nail plate is known as the cuticle or eponychium, serving as a protective seal for the nail.
Step-by-step explanation:
The dead tissue that tightly adheres to the natural nail plate is the cuticle, also known as the eponychium. The nail cuticle is a fold of epithelium that extends over the nail bed, playing a crucial role in protecting the nail matrix from pathogens and helping seal the edges of the nail. The nail matrix contains stem cells that divide to form keratinocytes, which produce keratin and make up the nail. Hence, the cuticle is important as it provides a protective seal for the nail growth center.