Final answer:
The nail plate is attached to the nail bed by the nail matrix, which is a thin layer of tissue. The nail matrix is responsible for nail growth and contains stem cells that produce keratin.
Step-by-step explanation:
The nail plate is attached to the nail bed by a thin layer of tissue called 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. It contains stem cells that divide to form keratinocytes, which are cells that produce keratin and make up the nail.