Lateral basal segmental bronchus of left lung

The lateral basal segmental bronchus of the left lung (B9) is one of the segmental bronchi arising from the left basal bronchial trunk that supplies the lateral basal segment (S9) of the left lower lobe. It is the airway that ventilates the laterally oriented portion of the basal pyramid of the left lower lobe, situated between the anterior basal segment (S8) anteriorly and the posterior basal segment (S10) posteriorly.

Anatomical details:

• The left lower lobe bronchus gives off the superior segmental bronchus (B6) first, then continues as the basal trunk, which divides into the basal segmental bronchi. The most common branching pattern is a bifurcation of the basal trunk (seen in ~75% of individuals), with a less common trifurcation pattern (~18%). [1]

• B9 typically arises as part of this basal division, along with the anteromedial basal bronchus (B7+8), which is often a combined segment on the left due to the cardiac impression) and the posterior basal bronchus (B10).

• The left lung commonly has four basal segments (anteromedial basal [S7+8], lateral basal [S9], and posterior basal [S10]), compared to five on the right, because the medial basal (S7) and anterior basal (S8) segments are frequently fused on the left side.

• The segmental artery (A9) generally accompanies B9, running toward the lung periphery relative to the bronchus, while the segmental vein (V9) runs more centrally.