Overview of Pulmonary Circulation

The pulmonary circulation transports deoxygenated blood from the right ventricle of the heart to the alveoli within the lungs. After exchanging gases, the oxygen-rich blood is carried from the alveoli back to the left atrium of the heart.

 This process starts with the pulmonary trunk emerging from the right ventricle carrying deoxygenated blood. As it arches over the upper edge of the heart, it branches into the left and right pulmonary arteries.

Upon entering the lungs, these arteries divide into lobar arteries, with three branches in the right and two in the left lung. These lobar arteries further branch extensively in both the lungs, forming smaller pulmonary arterioles.

These pulmonary arterioles supply the capillary networks around the alveoli. Here, the carbon dioxide from the blood is exchanged with the oxygen from the alveolar air.

This oxygenated blood then leaves the alveolar capillaries, entering small veins called venules.

The venules merge to form the four pulmonary veins, two from each lung, which finally empty into the left atrium, completing the pulmonary circuit.