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

Veins play a crucial role in the circulatory system by returning blood to the heart after it has circulated through the body. This function is essential for maintaining proper blood flow and ensuring that deoxygenated blood is sent back to the heart for re-oxygenation in the lungs. Unlike arteries, which are responsible for pumping oxygenated blood away from the heart to the tissues, veins operate under lower pressure and have valves that prevent backflow, facilitating the efficient return of blood. This process is vital for the overall function of the circulatory system, as it allows for the continuous cycle of blood movement needed to deliver oxygen and nutrients to tissues while removing carbon dioxide and waste products.