Bronchopulmonary Segments: Structural Architecture and Clinical Utility

Right Lung Segments (10 total)

The right lung is larger and invariably divided into three completely distinct lobes: the upper, middle, and lower. It contains a full complement of ten bronchopulmonary segments.

• Right Upper Lobe: Subdivided strictly into the Apical, Posterior, and Anterior segments. The posterior segment is a classic location for the reactivation of primary pulmonary tuberculosis.
• Right Middle Lobe: Located anteroinferiorly, it contains the Lateral and Medial segments. Due to its narrow, long, and poorly supported lobar bronchus, the middle lobe is uniquely highly susceptible to isolated collapse (Middle Lobe Syndrome).
• Right Lower Lobe: The largest lobe, subdivided into the Superior (apical), Medial basal, Anterior basal, Lateral basal, and Posterior basal segments. The superior segment frequently harbors posterior aspiration events.

Left Lung Segments (8-10 total)

The left lung is slightly smaller due to the massive cardiac notch and typically features only two lobes. Its bronchopulmonary segments are highly analogous to the right, though some apicoposterior branches often seamlessly fuse.

• Left Upper Lobe (including Lingula): Typically divided into the fused Apicoposterior, Anterior, Superior lingular, and Inferior lingular segments. The lingula is structurally part of the left upper lobe but functionally entirely represents the missing left middle lobe.
• Left Lower Lobe: Analagous to the right, containing the Superior (apical), fused Anteromedial basal, Lateral basal, and Posterior basal segments.