But it is, in fact, a form of protein called keratin, similar in composition to our finger and toenails.

Nails are made of a protein called keratin, and their growth is affected by several different factors, including age and health.

As skin cells die they form a barrier of dry protein called keratin.

The nails are made up of a protein called keratin.

The baleen filter is developed from different tissue, called keratin.

A claw is made of hard protein called keratin.

Hair is made of a tough protein called keratin.

They are made up of layers of a hardened protein called keratin, which is also in your hair and skin.

These particular cells are considered dead, and they're filled with a protein called keratin.

The shaft is mostly comprised of dead tissue and a protein called keratin.