Overview Bronchi left (primary) main bronchus divides into 2 (secondary) lobar bronchi supply 2 lobes of left lung right (primary) main bronchus divides into 2 secondary) lobar bronchi right upper lobe bronchus and bronchus intermedius (BI) BI divides into right middle lobe and right lower lobe bronchi supply 3 lobes of right lung each (secondary) lobar bronchus divides into several (tertiary) segmental bronchi RUL (3 segments): apical, posterior, anterior RML (2 segments): lateral, medial RLL (5 segments): superior, medial basal, anterior basal, lateral basal, posterior basal LUL (4 segments): apicoposterior, anterior, superior lingula, inferior lingula LLL (4 segments): superior, anteromedial basal, lateral basal, posterior basal Bronchopulmonary Segments independent respiratory units of lung each bronchopulmonary segment is supplied independently by: a (tertiary) segmental bronchus a tertiary branch of pulmonary artery carry low oxygen ("venous") blood to lungs for oxygenation a branch of bronchial artery