What is the primary component that makes up nails?

Nails are primarily composed of keratin, which is a type of protein that provides structure and durability. Keratin is a key structural material that makes up the outer layer of skin and forms the protective covering on hair and nails. The unique properties of keratin make nails strong and resilient, allowing them to withstand various physical stressors while also providing protection to the fingertips.

While collagen, calcium, and elastin are important for skin and overall health, they do not constitute the primary structure of nails. Collagen is primarily found in connective tissues, providing strength and elasticity. Calcium is crucial for bone health and plays a role in nail hardness but is not a component of the nail structure itself. Elastin contributes to the elasticity of skin and tissues but is also not a part of the nail. Therefore, keratin is the only choice that accurately represents the main substance that comprises nails.