Library · Physiology
Pulmonary circulation
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The pulmonary circulation is the circuit that carries blood from the heart to the lungs and back. It receives the entire cardiac output from the right side of the heart, meaning all of the blood that side pumps, and it works at low pressure and low resistance because its capillaries are arranged in parallel, many paths open at once instead of a single one.
Its vessels are different from those in the rest of the body. The pulmonary arteries have a wall one third as thick as that of their systemic counterparts, and a larger diameter. On the venous side, the veins join together to form the main pulmonary veins, which empty into the left atrium. It is a short, soft circuit, not the pressurized piping of the rest of the body.
That low pressure in the capillary is exactly what allows gases to be exchanged easily in the alveolus, the tiny sac where air and blood almost come into contact. There the blood loads up with oxygen for the rest of the body and unloads carbon dioxide.
In brief
The pulmonary circulation receives the entire cardiac output from the right side of the heart and is a low-pressure, low-resistance system.
A short, soft circuit, not a pressurized pipe like the rest of the body's.
Its arteries are one third as thick as their systemic counterparts and wider in diameter; its veins merge and empty into the left atrium.
That low capillary pressure eases gas exchange in the alveolus, where blood takes up oxygen and clears carbon dioxide.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Pulmonary Circulatory System, StatPearlsPublished
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