How does oxygen-rich blood travel from the lungs to the left atrium?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Silhouette diagram of the human body highlighting the heart and major blood vessels, with labeled arteries in red and veins in blue to show the structure of the cardiovascular system. — Circulatory system Human circulatory system.

After oxygen-rich blood is processed in the pulmonary capillaries of the lungs, it is collected into venules and then into progressively larger vessels known as the pulmonary veins.12

There are four pulmonary veins in total—two originating from the hilum of each lung. These veins serve as the primary conduits that transport the oxygenated blood directly to the left atrium of the heart. Once the blood enters the left atrium, it is prepared to be moved into the left ventricle for distribution throughout the body via systemic circulation.132