Final answer:
The nail matrix, located at the proximal end of the nail, is responsible for nail growth. Onychophagy, or nail biting, may increase blood flow to the nail matrix and potentially speed up nail growth.
Step-by-step explanation:
The nail matrix, which is a deep layer of living epidermal tissue at the proximal end of the nail, is responsible for nail growth. Stem cells in the nail matrix divide and produce keratinocytes, which make up the nail. As the nail grows longer, it forms first the nail root and then the nail plate. Onychophagy, or nail biting, can increase blood flow to the nail matrix and potentially cause the nail to grow faster.