Which vessel carries blood from the lungs to the left atrium?

• A. Aorta
• B. Pulmonary veins
• C. Pulmonary artery
• D. Superior vena cava

Answer: (B)

Blood returns from the lungs to the heart through the pulmonary veins. After gas exchange, oxygen-rich blood travels via these veins and enters the left atrium, then moves to the left ventricle to be pumped out to the body. This is a notable exception to the general rule that veins carry deoxygenated blood, because the pulmonary veins carry oxygenated blood back to the heart. The other vessels have different roles: the aorta carries blood from the left ventricle to the body, the pulmonary artery carries deoxygenated blood from the right ventricle to the lungs, and the superior vena cava brings deoxygenated blood from the upper body to the right atrium.