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Why does pulmonary circulation operate at a lower pressure than systemic 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.

Pulmonary circulation operates at a significantly lower pressure than systemic circulation to facilitate efficient gas exchange without causing damage to the delicate tissues of the lungs.1

Because the primary function of this circuit is to transport blood to the alveoli for the exchange of oxygen and carbon dioxide, the structural integrity of the pulmonary vessels is adapted to this low-pressure environment. Specifically, the pulmonary arteries are much flimsier than systemic arteries of a similar size, as their wall structure is determined by the lower intravascular pressure they experience—on average, this pressure is five times lower than that found in systemic arteries.12

Maintaining this lower pressure is essential for protecting the lung's fine capillary networks, which are necessary for effective respiration.1