Here's a breakdown:
* Epithelial tissue is a type of tissue that covers the surfaces of the body, both inside and out. It's characterized by closely packed cells arranged in layers. It's main functions are for protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception.
* Keratin is a fibrous structural protein that is also the key structural component of hair, and the outer layer of skin.
* Nails are accessory structures of the skin, made of layers of dead, hardened keratinocytes. The nail matrix, located at the base of the nail, is responsible for nail growth. Matrix cells are specialized epithelial cells that produce keratin, which then hardens and forms the nail plate.
In summary, while nails are formed by specialized epithelial cells that produce keratin, the nail itself is primarily composed of hardened keratin, not epithelial tissue.