Lateral basal segmental artery of left lung

The lateral basal segmental artery of the left lung (A9), is a branch of the left inferior (interlobar) pulmonary artery that supplies the lateral basal segment (S9) of the left lower lobe.

Anatomical Definition

The lateral basal segmental artery (A9) arises from the basal trunk of the left pulmonary artery after it gives off the superior segmental artery (A6). It accompanies the lateral basal segmental bronchus (B9) and supplies the lateral basal bronchopulmonary segment (S9) of the left lower lobe. This segment occupies the lateral aspect of the base of the left lower lobe, bordered by the anterior basal segment (S8) anteriorly, the posterior basal segment (S10) posteriorly, and the medial basal segment (S7) medially.

Origin and Course

The left main pulmonary artery is a direct posterior continuation of the main pulmonary trunk and runs in the interlobar fissure on the left side, with a variable branching pattern. After giving off branches to the upper lobe and lingula, the interlobar artery continues inferiorly as the basal trunk. The basal trunk typically bifurcates or trifurcates to give rise to the individual basal segmental arteries, including A7 (medial basal), A8 (anterior basal), A9 (lateral basal), and A10 (posterior basal). A9 generally lies toward the lung periphery (laterally) relative to its corresponding bronchus B9.

Key Anatomical Features

• The segmental arteries of the lower lobe may be single, duplicate, or even triplicate, with variation from the dominant pattern occurring in as many as 20% of cases.

• In the left lung, A7 is often diminutive due to the cardiac silhouette and is frequently supplied as a subsegmental branch off A8.

• The segmental artery closely accompanies the segmental bronchus in approximately 90% of pulmonary segments.

• Within the segments, the arteries generally lie toward the lung periphery relative to their corresponding bronchi (anterior, lateral, or posterior), while the segmental veins lie central to the bronchi (posterior, medial, or anterior).

• Fifteen anatomic variations in the vasculature of the left lower lobe basal segments have been described on 3D CT angiography.