Final answer:
Nails that have fallen off due to injury or infection often grow back if the nail bed is intact, as nails continuously grow from the nail bed throughout life. However, severe damage to the nail bed may prevent regrowth, potentially leading to permanent nail loss.
Step-by-step explanation:
The student's question pertains to whether a fingernail or toenail, once lost, will be missing permanently. Generally, nails are made up of specialized epidermal cells filled with keratin. When injury or infection causes a nail to fall off, the nail can often grow back if the nail bed is not severely damaged. Fingernails and toenails grow from the nail bed, and this growth process continues throughout an individual's life, with rates of growth influenced by factors such as age, sex, and season.
Nails serve several important functions, including protecting the fingertips and enhancing sensation when handling objects. In addition, they act as a counterforce to sensitive fingertips. The regrowth of nails depends on the health and integrity of the nail bed and surrounding tissues. Typically, if the nail bed is intact, nails will regrow over time. However, if the nail bed has been severely damaged, this can interfere with the regrowth process, potentially leading to permanent nail loss.