What substance is referred to by the term "Keratin"?

Keratin is accurately described as an extremely tough protein substance primarily found in hair, nails, and the outer layer of skin. This fibrous structural protein serves a crucial role in providing strength and protection to these tissues. The hardness and resilience of keratin enable it to withstand various mechanical stresses, making it essential for protective functions in the body.

In hair and nails, keratin contributes to their durability and structure, while in the skin, it helps form a barrier against environmental damage. This unique property of keratin differentiates it from other proteins that may be softer or more fluid, reflecting its specialized role in the body's anatomy.