|Air enters the lungs through the trachea
At the lung the trachea branches into several bronchi (2) which branch into smaller vessels until they terminate in alveoli.
Deoxygenated blood is transported from the head, neck and arms to the heart by the anterior vena cava (1) . The posterior vena cava and azygous (not shown) also transport deoxygenated blood to the heart. This blood passes through the right side of the heart and is carried to the lung for oxygenation in the pulmonary artery (2). This is the only artery that carries highly deoxygenated blood. After being oxygenated it returns to the heart in the pulmonary vein (3). This is the only vein that carries highly oxygenated blood.
In this picture of the right lung the pulmonary vein in not injected so it appears as a dark brown vessel.
Follow the pathway of the blood from the heart into the lungs.
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