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What route does blood take through the heart, lungs, and body during a complete circulation?

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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.

Blood circulation in the human body follows a continuous, dual-circuit path consisting of the pulmonary circulation and the systemic circulation.12

The Pulmonary Circuit

The cycle begins when oxygen-poor blood returns from the body to the right atrium of the heart via the superior and inferior venae cavae. From there, the blood flows into the right ventricle, which pumps it into the pulmonary artery. This artery carries the deoxygenated blood to the lungs, where it moves through smaller vessels into capillaries surrounding the alveoli. Here, carbon dioxide is released and oxygen is absorbed.3214

The Systemic Circuit

The now oxygen-rich blood travels through the pulmonary veins back to the left atrium of the heart. It then passes into the left ventricle, which pumps the blood into the aorta. The aorta distributes this oxygenated blood through a branching network of arteries and arterioles to the body's tissues. After oxygen and nutrients are exchanged for waste products in the capillaries, the blood returns to the heart through venules and veins, completing the circuit.4132