Apical segment of right lung

The apical segment of the right lung (S1) is the most superior bronchopulmonary segment of the right upper lobe. It occupies the apex (dome) of the right lung and is bounded by the posterior and anterior segments of the right upper lobe inferiorly.

Key anatomical features:

• Bronchus: The apical segmental bronchus (B1) is one of three segmental bronchi arising from the right upper lobe bronchus. The most common branching pattern is a trifurcation of the right upper lobe bronchus into the apical (B1), posterior (B2), and anterior (B3) segmental bronchi, seen in approximately 64% of individuals. A bifurcated pattern, where B1 shares a common trunk with either B2 or B3, occurs in the remainder.

• Arterial supply: The apical segmental artery (A1) typically arises from the truncus anterior (the first branch of the right pulmonary artery at the hilum), often sharing a common trunk with the anterior segmental artery (A3).

• Venous drainage: The apical segment is drained by branches of the superior pulmonary vein, with the intersegmental vein (V1b) serving as a key landmark for identifying the intersegmental plane during segmentectomy.

• Surface anatomy: The apical segment projects above the level of the first rib and clavicle, forming the lung apex that extends into the root of the neck. The apical pleura overlying this segment can be a site of pathology including apical caps (subpleural scarring), Pancoast tumors, and tuberculosis.