A human red blood cell in an artery of the left arm is on its way to deliver oxygen to a cell in the thumb. To travel from the artery in the arm to the left ventricle, this red blood cell must pass through

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A red blood cell in an artery of the left arm must first travel through one capillary bed in the thumb before entering a vein. This vein leads to the subclavian vein, which then leads to the superior vena cava, which ultimately delivers blood to the right atrium of the heart. From the right atrium, the blood travels to the right ventricle and is then pumped into the pulmonary artery, which takes the blood to the lungs for oxygenation. After oxygenation, the blood returns to the heart via the pulmonary vein and enters the left atrium. Finally, the blood travels to the left ventricle, which pumps it out through the aorta, leading to the rest of the body. Therefore, the red blood cell must pass through two capillary beds (in the thumb and in the lungs) before reaching the left ventricle.

A Human Red Blood Cell in an Artery of the Left