Which protein is primarily responsible for the pliability of the skin?

The primary protein responsible for the pliability of the skin is elastin. Elastin is a vital structural protein that allows tissues in the body to resume their shape after stretching or contracting. It is particularly important in the skin, where it provides the necessary elasticity that enables the skin to stretch and then return to its original state. This quality is crucial for maintaining youthful skin texture and preventing sagging.

While collagen is also present in the skin and provides strength and structure, it does not contribute to pliability to the same extent as elastin. Keratins are primarily protective proteins found in the outer layers of the skin and hair, providing a barrier and structure, but they are not involved in skin pliability. Fibronectin plays a role in cell adhesion and tissue repair but does not have a direct influence on the skin’s flexibility. Therefore, elastin is the correct choice for its specific role in ensuring the skin's ability to stretch and maintain its form.