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What are the two major circuits of the human cardiovascular system?

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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.

The human cardiovascular system is composed of two major circuits that work together to transport blood throughout the body:

Pulmonary circulation: This circuit carries oxygen-depleted blood from the heart to the lungs, where it releases carbon dioxide and replenishes its oxygen supply before returning to the heart.12
Systemic circulation: This circuit transports oxygen- and nutrient-rich blood from the heart to the rest of the body's tissues and returns oxygen-depleted blood back to the heart.32

Together, these circuits form a closed system propelled by the heart, ensuring that oxygen, nutrients, and hormones are delivered to cells while metabolic waste products are efficiently removed.24