What is the primary function of veins in the cardiovascular system?

The primary function of veins in the cardiovascular system is to return deoxygenated blood to the heart. Veins are responsible for collecting blood that has circulated through the body, where it has delivered oxygen and nutrients to tissues. After this exchange, the now deoxygenated blood, which is rich in carbon dioxide and other waste products, is transported back to the heart via the veins.

This process is critical for maintaining the overall circulation of blood in the body, allowing for the re-oxygenation of blood in the lungs before it is pumped back out to the rest of the body through the arteries. The structure of veins, which includes valves to prevent backflow and a thinner muscular layer compared to arteries, facilitates this return journey against lower pressure, ensuring the efficient movement of blood back to the heart.

While the other choices reflect important aspects of the cardiovascular system, they do not accurately describe the primary role of veins.