Blood vessels carry blood from the ____ back to the heart.

Blood vessels are integral to the circulatory system, facilitating the transport of blood throughout the body. The correct answer identifies veins as the blood vessels responsible for carrying deoxygenated blood back to the heart. After the blood has delivered oxygen and nutrients to tissues and has picked up carbon dioxide and waste products, it enters the venous system. Veins have a one-way valve system that prevents backflow and ensures that blood flows in the right direction toward the heart.

In an overall context, the lungs are involved in oxygenating blood before it returns to the heart, but they do not serve as direct return vessels; rather, blood coming from the lungs travels back to the heart via the pulmonary veins. The aorta is the largest artery in the body that carries oxygen-rich blood away from the heart to the rest of the body, while arteries are responsible for carrying blood away from the heart. However, veins specifically are key in returning blood to the heart, making them the correct designation in this context.