Citation:
Keratin is a tough, fibrous protein that forms the primary structural component of hair, nails, and the outer layer of skin. It provides protection against abrasion and water loss.
The outermost layer of skin that contains keratinized cells to protect the body against external environment.
Hair follicle: A small tubular cavity containing the root of a hair, in which keratin is produced to form hair.
Nail bed: The skin beneath the nail plate that contains nerves and blood vessels; it supports the nail plate as it grows and is protected by keratin