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

The primary function of veins in the circulatory system is to carry deoxygenated blood towards the heart. This is important because, after oxygen has been delivered to the tissues and organs by the arteries, the blood that returns to the heart must be reoxygenated in the lungs before it can be redistributed throughout the body. Veins are designed with thinner walls and larger lumens compared to arteries, allowing them to hold a greater volume of blood and facilitate this return flow. Additionally, veins contain valves that help prevent the backflow of blood, ensuring that it moves efficiently back to the heart despite the lower pressure compared to arteries. This role is vital for maintaining proper circulation and supporting overall cardiovascular health.