What is the primary type of blood vessel that carries blood back to the heart?

Veins are the primary type of blood vessel that carries blood back to the heart. They are specifically designed to return deoxygenated blood from the body’s tissues to the heart, where it can be re-oxygenated in the lungs. The structure of veins includes thinner walls and larger diameters compared to arteries, allowing them to accommodate the lower pressure of blood returning to the heart. Veins also contain one-way valves that prevent the backflow of blood, ensuring it flows in the correct direction toward the heart.

In contrast, arteries carry oxygen-rich blood away from the heart to the rest of the body under higher pressure. Capillaries are small blood vessels where the exchange of oxygen, carbon dioxide, nutrients, and waste products occurs between blood and tissues. Venules are small vessels that collect blood from capillaries and merge to form veins, but they do not have the same role in returning blood to the heart as veins do. Thus, veins are distinctly responsible for returning blood to the heart, making them the correct answer.