cortices. 1  1a (1) : the outer or superficial part of an organ or bodily structure (such as the kidney, adrenal gland, or cerebellum or a bone); especially : cerebral cortex (2) : the proteinaceous usually pigmented layer of a hair below the cuticleb : the outer part of some organisms (such as paramecia)
If a toenail has completely fallen off, it can take up to 18 months for it to grow back. A toenail can take longer to grow back if the nail bed has permanent damage. In some cases, old nails do not completely fall off, and they act as a protective...
Luckily, scientists have. Fingernails grow a little over twice as quickly as toenails: an average rate of 3.47 mm/month compared to 1.62 mm/month [1]. Nails evolved from claws about 55 million years ago, and are one of the features that distinguish primates [2].