Human Anatomy - Kotsan I. Ya. 2009

Vessels of the Lesser (Pulmonary) Circulation
Pulmonary veins

The pulmonary capillaries give rise to venules, which merge into progressively larger Veins and ultimately form two pulmonary veins in each lung. Each pair consists of a superior and an inferior pulmonary vein (vv. pulmonales superior et inferior), which run horizontally and empty through separate orifices into the left atrium. The right pulmonary veins are longer than the left ones; they lie inferior to the right pulmonary artery, posterior to the SUPERIOR VENA CAVA and the ascending aorta, whereas the left pulmonary veins pass anterior to the descending aorta. The pulmonary veins lack Valves.

The right superior pulmonary vein (v. pulmonalis superior dextra) collects Blood not only from the superior lobe but also from the middle lobe of the right lung. Blood drains from the superior lobe of the right lung via three branches: the apical, anterior, and posterior branches (rr. apicalis, anterior et posterior). Each of these is formed by the merger of two components: the apical branch consists of an intrasegmental part (pars intrasegmentalis) and an intersegmental part (pars intersegmentalis); the anterior branch consists of an intrasegmental part (pars intrasegmentalis) and an intersegmental part (pars intersegmentalis); and the posterior branch consists of an infralobular part (pars infralobaris) and an interlobular part (pars intralobaris). Blood drainage from the middle lobe of the right lung occurs through the middle lobe branch (r. lobi medii), which is formed by two components: a lateral part (pars lateralis) and a medial part (pars medialis).

The right inferior pulmonary vein (v. pulmonalis inferior dextra) collects blood from the five segments of the inferior lobe of the right lung: the apical segment and the basal segments—medial, lateral, anterior, and posterior. Blood drains from the apical segment via the apical (superior) branch (r. apicalis (superior)), which is formed by the merger of two components: an intrasegmental part (pars intrasegmentalis) and an intersegmental part (pars intersegmentalis). Blood from all the basal segments drains via a common basal vein (v. basalis communis), which is formed by the superior and inferior basal veins (vv. basales superior et inferior). The common basal vein merges with the apical (superior) branch of the inferior lobe to form the right inferior pulmonary vein.

The left superior pulmonary vein (v. pulmonalis superior sinistra) collects blood from the segments of the superior lobe of the left lung. It has three branches (tributaries): the apicoposterior, anterior, and lingular branches (rr. apicoposterior, anterior et lingularis). Each of these is formed by the merger of two components: the apicoposterior branch consists of an intrasegmental part (pars intrasegmentalis) and an intersegmental part (pars intersegmentalis); the anterior branch consists of an intrasegmental part (pars intrasegmentalis) and an intersegmental part (pars intersegmentalis); and the lingular branch consists of a superior part (pars superior) and an inferior part (pars inferior).

The left inferior pulmonary vein (v. pulmonalis inferior sinistra) collects blood from the inferior lobe of the left lung (including the apical and all basal segments). An apical branch (r. apicalis) arises from the apical segment of the inferior lobe and is formed by the merger of two components: an intrasegmental part (pars intrasegmentalis) and an intersegmental part (pars intersegmentalis). Blood drains from all the basal segments of the inferior lobe of the left lung via a common basal vein (v. basalis communis), which is formed by the merger of the superior and inferior basal veins (vv. basales superior et inferior). The fusion of the apical branch and the common basal vein forms the left inferior pulmonary vein.