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

The primary function of veins in the circulatory system is to return deoxygenated blood to the heart. This is a crucial role because, after blood has circulated through the body, it has delivered oxygen and nutrients to tissues and picked up carbon dioxide and other waste products. Veins are equipped with valves that help prevent backflow and ensure the efficient return of blood to the heart, where it can be sent to the lungs for oxygenation.

This function is vital for maintaining proper circulation and ensuring that the body's tissues receive a continuous supply of oxygen and nutrients. The structure of veins, which are typically thinner and have a lower pressure compared to arteries, is adapted for this task, making them well-suited to carry blood back to the heart effectively.