The pulmonary circulation includes the pulmonary arteries and veins.

The main pulmonary artery (also known as the pulmonary trunk) is a short vessel that arises from the infundibulum of the right ventricle of the heart, passes posteriorly and slightly upwards, and below the aortic arch divides into the left and right pulmonary arteries.

The right pulmonary artery passes posteriorly and near the hilum divides into superior, middle, and inferior branches, supplying the upper, middle, and lower pulmonary lobes.
The left pulmonary artery passes posterosuperiorly, enters the hilum of the left lung, and divides into superior and inferior branches, which supply the superior and inferior lobes. The left pulmonary artery also has a singular branch supplying the lingula.

Further, these branches divide into pulmonary capillaries that form a network around the alveoli.

The pulmonary veins are two on each side, and they carry oxygenated blood from the lungs to the heart.

They arise from the pulmonary capillaries that join together.

Capillaries form the intrasegmental veins, which unite and create the segmental veins. Segmental veins merge, forming the intersegmental veins, which combine in lobar veins.

The right lung has three lobar veins, while the left lung - two.

Lobar veins merge, forming the pulmonary veins, which drain the parenchyma of the lungs.

The pulmonary veins emerge from each lung at the hilum and drain into the left atrium of the heart.

On their course, the pulmonary veins also receive the bronchial veins.

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Pulmonary circulation