Bronchopulmonary Segments

Mnemonic

“10 on the right, 8 to 10 on the left”:

• Right upper lobe - apical, posterior, anterior (3)
• Right middle lobe - lateral, medial (2)
• Right lower lobe - apical (superior), medial basal, anterior basal, lateral basal, posterior basal (5)
• Left upper lobe - apicoposterior, anterior, superior lingular, inferior lingular (4)
• Left lower lobe - apical, anteromedial basal, lateral basal, posterior basal (4)

The left has fewer because segments fuse, apical with posterior and medial with anterior basal, since the heart occupies the space.

Each segment has its own segmental bronchus and artery but its veins run between segments, which is what makes segmentectomy anatomically possible.

The apical segment of the lower lobe and the posterior segment of the upper lobe are the aspiration sites when supine, because the right main bronchus is wider, shorter and more vertical.

Expansion

• Right lung - 10 segments: 3 upper lobe, 2 middle lobe, 5 lower lobe
• Left lung - 8 to 10 segments, since the apical and posterior segments commonly fuse as the apicoposterior segment, and the anterior and medial basal segments as the anteromedial basal segment

A bronchopulmonary segment is a pyramidal unit with its apex at the hilum and its base at the pleural surface. Because each is functionally and structurally independent, a diseased segment can be resected without compromising its neighbours.

The superior segment of the lower lobe deserves special note: it is the most dependent segment in a supine patient, and therefore a classic site for aspiration pneumonia.