Posterior segment of right lung

The posterior segment of the right lung (S2) is one of the three bronchopulmonary segments of the right upper lobe. It is a discrete, anatomically and functionally independent unit of lung parenchyma, defined by its own segmental bronchus (B2), segmental artery (A2), and segmental vein.

Anatomical characteristics:

• Location: S2 occupies the posterolateral portion of the right upper lobe, situated between the apical segment (S1) superiorly and the anterior segment (S3) anteriorly. Its posterior surface lies against the posterior chest wall.

• Bronchus (B2): The posterior segmental bronchus arises from the right upper lobe bronchus. In the most common branching pattern (trifurcated, ~64% of cases), B1, B2, and B3 arise as three separate branches; in bifurcated variants (~22%), B1 and B2 may share a common trunk (B1+2). The subsegmental branches are B2a (apical subsegment) and B2b (posterior subsegment).

• Arterial supply (A2): The posterior segmental artery typically arises distal to the truncus anterior (which supplies S1 and S3), often from the ascending or recurrent branch of the right pulmonary artery. In some cases, S2 receives a dual arterial supply from both the superior and inferior arterial trunks.

• Venous drainage: The lateral branch of the posterior segmental vein of the upper lobe serves as an important anatomical landmark, demarcating the boundary between the anterior and posterior segments.

• Intersegmental boundaries: The boundaries between S2 and adjacent segments (S1 and S3) are defined by intersegmental planes through which the intersegmental veins course.