What is the primary function of the circulatory system?

The primary function of the circulatory system is to transport blood, nutrients, gases, and wastes throughout the body. This system plays a crucial role in maintaining homeostasis by ensuring that all cells receive the oxygen and nutrients they need to function properly while also removing carbon dioxide and metabolic wastes.

Blood acts as the medium through which these substances circulate, moving from the heart to various tissues and organs via a network of blood vessels. The systematic and pulmonary circuits enable effective delivery of oxygen from the lungs to the tissues and then return deoxygenated blood to the heart for re-oxygenation, exemplifying the comprehensive role the circulatory system plays in overall bodily function.

While the other options describe processes that the body engages in—like gas exchange in the lungs, digestion, and thermoregulation—none encompass the broad and integrative role that the circulatory system has in transporting vital materials throughout the entire body.