Keratin is a type of protein found in which parts of the body?

Keratin is a fibrous protein that serves as a key structural component in various parts of the body, particularly in the integumentary system. The correct choice highlights the fact that keratin is prominently found in hair, skin, and nails.

In hair, keratin contributes to its strength and resilience, allowing it to withstand various environmental factors. In the skin, keratin forms a protective barrier, helping to prevent dehydration and safeguard against environmental damage. Additionally, keratin is also a major component of nails, providing them with durability and strength.

Other options mention incorrect locations for keratin. For instance, while skin is correctly identified in other choices, muscles, blood, bone, and fat do not have keratin as a significant component. This delineation is crucial for understanding the role of keratin in maintaining the integrity and function of hair, skin, and nails.