Segmental arteries of the lungs

At a glance

English

Segmental arteries of the lungs

Latin (TA2)

Arteriae segmentales pulmonum

System

Artery

Region

Thorax

In order

From the apical segmental artery of right lung to the posterior basal segmental artery of left lung

About the segmental arteries of the lungs

The segmental arteries are the branches of the right and left pulmonary arteries that supply the individual bronchopulmonary segments of the lungs. Each segment is a self-contained wedge of lung with its own segmental bronchus and its own artery, separated from neighbouring segments by thin sheets of connective tissue. The arteries carry deoxygenated blood from the right ventricle to the alveolar capillaries, so, unusually for arteries, the blood in them is low in oxygen.

All members share one rule of position: each artery runs with its bronchus through the centre of the segment, branching as the airways branch. This contrasts with the segmental veins, which lie between segments. The arteries are thin-walled and elastic, because pressure in the pulmonary circulation is much lower than in the systemic one. The nutrition of the bronchial walls themselves comes from the separate bronchial arteries of the aorta, not from these vessels. Each segmental artery divides repeatedly in step with the bronchial tree, so that a branch accompanies every airway down to the respiratory bronchioles. Beyond this point the vessels break up into the capillary network around the alveoli, where gas exchange takes place. The arteries are named after the segments they supply, and therefore follow the same naming as the segmental bronchi.

The arrangement follows the lobes. The right pulmonary artery gives a large anterior trunk to the upper lobe, which supplies the apical and anterior segments, with further branches to the posterior segment. The artery then continues down as the interlobar part, giving the medial and lateral arteries of the middle lobe, a superior artery to the top of the lower lobe and four basal arteries (medial, anterior, lateral and posterior). The left pulmonary artery arches over the left main bronchus and gives a variable number of branches to the apical, posterior and anterior parts of the upper lobe and to the lingula; it then descends behind the bronchus to give a superior artery and the basal arteries to the lower lobe. On the left the medial basal segment is usually merged with the anterior basal segment, and its artery may arise in common.

Variation in the number and origin of upper lobe branches is common, especially on the left, and must be identified before lobectomy or segmentectomy. Because each segment has its own artery and bronchus, a pulmonary embolus lodging in a segmental artery produces a wedge-shaped area of damaged or poorly perfused lung, and a segment with disease can be removed while leaving the rest of the lobe working.