How do veins differ from arteries in structure and function?

Veins are characterized by having thinner walls compared to arteries, which enables them to be more flexible and accommodate varying volumes of blood. The larger lumens of veins allow for greater blood capacity as they transport blood back to the heart, often under lower pressure than that found in arteries. This structural adaptation is crucial for their function in the circulatory system.

Additionally, veins typically contain valves that help prevent the backflow of blood, ensuring that it flows in one direction toward the heart. This is particularly important in the limbs, where blood must travel against gravity. The combination of thinner walls, larger lumens, and the presence of valves distinguishes veins from arteries, which have thicker, more muscular walls designed to withstand the higher pressure of blood being pumped directly from the heart.