What is the primary function of keratin in the skin?

Keratin is a key structural protein in the skin, primarily serving the function of offering protection. It forms a tough, protective layer that helps to shield underlying tissues from environmental damage, such as pathogens, chemicals, and mechanical injury. This protective barrier is crucial because it prevents the entry of harmful substances and helps to reduce water loss, maintaining overall skin health.

While other functions, such as regulating temperature, providing elasticity, and facilitating sensation, are important in the context of skin physiology, they are not the primary roles of keratin. For instance, temperature regulation is primarily managed by blood vessels and sweat glands, while elasticity is mainly attributed to proteins like collagen and elastin. Sensory functions are carried out by nerve endings in the skin. Therefore, the primary role of keratin is to protect the skin, making the correct answer the one that highlights this essential function.