What protein composes the hair and skin?

Keratin is the primary structural protein found in hair, skin, and nails. It provides strength and resilience to these tissues, helping protect them from damage and maintain their integrity. In the skin, keratin forms a barrier that helps prevent water loss and shields against environmental factors. In hair, keratin makes up the hair strands, contributing to their strength and overall structure.

Collagen, while an important protein for skin elasticity and structure, does not make up hair or skin in the same way keratin does. Elastin provides flexibility and resilience but is more relevant to the elasticity of tissues rather than forming the structural component of hair and skin. Myoglobin is a protein found in muscle tissue that binds oxygen, which is unrelated to the composition of hair and skin. Thus, keratin stands out as the correct choice due to its unique role in forming and maintaining these protective outer layers of the body.