Right and Left Principal Bronchi — Comparison
Origin
Both arise from the carina — the bifurcation of the trachea at the level of the lower border of T4 (sternal angle / angle of Louis).
Comparison Table
| Feature | Right Principal Bronchus | Left Principal Bronchus |
|---|---|---|
| Length | ~2.5 cm (shorter) | ~5 cm (longer) |
| Width | Wider | Narrower |
| Angle with trachea | ~25° (more vertical) | ~45° (more oblique) |
| Direction | More in line with trachea | More horizontal |
| Lobar bronchi | 3 (superior, middle, inferior) | 2 (superior, inferior) |
| Eparterial bronchus | Present (right superior lobar bronchus lies above pulmonary artery) | Absent |
| Foreign body tendency | More common (wider, more vertical) | Less common |
Eparterial Bronchus (Right Side)
The right superior lobar bronchus is also called the eparterial bronchus because it arises from the right principal bronchus above (epi = above) the right pulmonary artery.
All other lobar bronchi arise below (hypo) the pulmonary artery — hence called hyparterial bronchi.
On the left side, there is no eparterial bronchus — the left superior lobar bronchus arises below the left pulmonary artery.
Clinical Significance
Foreign body aspiration:
- Foreign bodies and aspirated materials preferentially enter the right principal bronchus because it is shorter, wider, and more vertical (more in line with the trachea)
- Right-sided aspiration is therefore more common
- In the supine position: aspirated material enters the superior (apical) segment of the right lower lobe — the most dependent segment in this position
- In the erect/sitting position: aspirated material enters the right lower lobe basal segments
Carina:
- The point where the trachea bifurcates into the two principal bronchi
- Highly sensitive area — stimulation causes cough reflex
- Widening of the carina (angle > 70°) on chest X-ray/bronchoscopy suggests enlargement of subcarinal lymph nodes (e.g., malignancy, tuberculosis)