Segmental pulmonary veins

At a glance

English

Segmental pulmonary veins

Latin (TA2)

Venae segmentales pulmonum

System

Vein

Region

Thorax

In order

From the apical vein of right lung to the inferior basal vein of left lung

About the segmental pulmonary veins

The segmental pulmonary veins carry freshly oxygenated blood out of the bronchopulmonary segments, the wedge-shaped units into which each lung is divided. They are the first named tributaries of the pulmonary veins, which usually leave each lung as a superior and an inferior vein and open into the left atrium. Together with the segmental arteries and bronchi they make up the internal plumbing of every segment.

Their most important shared feature is where they run. A segmental artery travels with its bronchus through the centre of a segment, but the veins do not. Their small tributaries begin in the alveolar capillaries and run in the connective tissue between neighbouring segments, so each named vein drains parts of two adjacent segments and marks the plane between them. Only as they approach the hilum do the veins gather into larger trunks and converge on the pulmonary veins. Like other pulmonary veins they have no valves. Because they collect from the borders of segments, small veins also run just beneath the visceral pleura on the lung surface, and some receive blood from the walls of the smaller bronchi. Their pattern is less regular than that of the arteries, which follow the airways closely.

The pattern differs between the lungs. In the right upper lobe, apical, anterior and posterior veins drain the three segments of that lobe, and the middle lobe is drained by a lateral and a medial vein, often united as a middle lobe vein; all of these usually join the superior right pulmonary vein. In the left upper lobe an apicoposterior vein and an anterior vein drain the upper part, while the lingula is drained by superior and inferior lingular veins that may join as a single lingular vein before entering the superior left pulmonary vein. In each lower lobe a superior vein drains the apex of the lobe, and the basal segments drain into superior and inferior basal veins, which commonly form a common basal vein; these feed the inferior pulmonary vein of their side.

Variation is frequent, both in how these tributaries combine and in the number of veins reaching the atrium; a separate middle lobe vein on the right is a common example. Knowing that veins lie between segments is the key to segmentectomy, in which a surgeon removes a single segment along its venous planes while sparing neighbouring lung. The openings of the pulmonary veins into the left atrium are also where many rhythm disturbances begin, which is why they are targeted during ablation for atrial fibrillation.