lungkretsloppet

Lungkretsloppet, or the pulmonary circulation, is the portion of the cardiovascular system that carries blood between the heart and the lungs for gas exchange. It forms a distinct circuit that operates in parallel with the systemic circulation.

Deoxygenated blood is returned to the heart via the venae cavae and enters the right atrium, moves to the right ventricle, and is pumped into the pulmonary trunk. The trunk divides into the left and right pulmonary arteries, which branch through the lungs to arterioles and capillaries surrounding the alveoli. In the pulmonary capillaries, carbon dioxide is released from the blood and oxygen is picked up. Oxygenated blood then returns to the left atrium via the pulmonary veins.

Compared with the systemic circuit, the lung circulation operates at a lower pressure and has a large, highly compliant vascular bed. The thin-walled arteries and extensive capillary network facilitate efficient gas exchange and help accommodate changes in blood flow with varying breathing demands.

Regulation of the pulmonary circulation involves autonomic nerves and local mediators that adjust vessel tone. A key mechanism is hypoxic vasoconstriction, which redirects blood toward better-ventilated regions of the lung. Clinically, disturbances in lung circulation—such as pulmonary hypertension, pulmonary embolism, or edema—can impair gas exchange and place altered strain on the heart.