Which human blood vessels carry oxygen-rich blood from the lungs to the heart?

The pulmonary veins carry oxygen-rich blood from the lungs to the heart.

Usually, four pulmonary veins return blood to the left atrium: two from each lung. Blood becomes oxygenated in the lung capillaries after carbon dioxide is released into the air spaces and oxygen diffuses into the bloodstream.

The pulmonary veins are an important exception to the simplified rule that veins carry oxygen-poor blood. Anatomically, a vein is a vessel that carries blood toward the heart, while an artery carries blood away. Therefore, pulmonary veins are still veins even though they normally contain oxygen-rich blood.

The pulmonary arteries create the opposite exception. They carry oxygen-poor blood from the right ventricle to the lungs. After the left atrium receives blood from the pulmonary veins, it passes through the mitral valve into the left ventricle, which pumps it into the aorta for systemic circulation.