Left main bronchus
Main bronchi · About 45 degrees About 5 cm Under aortic arch
Narrower, longer (about 5 cm) and more horizontal (about 45 degrees) than the right. It passes below the arch of the aorta and in front of the oesophagus and descending aorta to the left hilum at T5 to T6, where it divides into the upper and lower lobe bronchi.
Traced from the start
- Trachea
- Left main bronchus
Detail
- Dimensions
- About 5 cm long, about 45 degrees from the midline, smaller calibre than the right
- Relations
- Aortic arch above; descending aorta and oesophagus behind; left pulmonary artery arches over it so the upper lobe bronchus is hyparterial; left atrium below
- Branches
- Left upper lobe bronchus (upper division and lingular division) and left lower lobe bronchus; no bronchus intermedius on the left
- Nearby nerve
- Left recurrent laryngeal nerve hooks under the aortic arch beside the ligamentum arteriosum just above it
When it goes wrong
Left atrial enlargement
Left main bronchus elevated and pushed backwards, splaying the carina; severe enlargement can compress it and collapse the left lower lobe
Aortic arch aneurysm or subaortic mass
Extrinsic compression of the left main bronchus with left lung collapse, often with hoarseness from left recurrent laryngeal nerve palsy
One-lung ventilation for thoracic surgery
The long, uniform left main bronchus is the usual site for a left-sided double-lumen tube; on the right the upper lobe bronchus arises too close to the carina
Practise this structure
3 questions in the bank tagged Thorax.
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