Left main bronchus
Citation, DOI & article data
The trachea bifurcates into the right and left main bronchi at the level of the carina, supplying air to the right and left lungs respectively. Each main or primary bronchus enters the hilum of its lung and gives rise to secondary lobar bronchi, which further divide into tertiary segmental bronchi supplying the individual bronchopulmonary segments.
The left main bronchus is longer, runs more horizontally (40 degrees to the median plane) 3 and is about twice as long as the right main bronchus 1,2. It reaches the hilum of the left lung at the level of T6, lying inferior to the aortic arch and anterior to the esophagus and thoracic aorta.1,2 It is about 5 cm long and 1.2 cm in diameter.3
It gives rise to two lobar bronchi, the left upper and lower lobar bronchi 1.
At left pulmonary hilum:
- superiorly: left pulmonary artery (aortic arch superior to pulmonary artery)
- inferiorly: left pulmonary veins
- anteriorly: left pulmonary veins
- posteriorly: descending thoracic aorta
The left main bronchus is most often elliptic in shape on its cross section.4
- 1. Applied Radiological Anatomy. Cambridge University Press. ISBN:0521766664. Read it at Google Books - Find it at Amazon
- 2. Dalley AF, Agur AM. Clinically Oriented Anatomy. Lippincott Williams & Wilkins. ISBN:1605476528. Read it at Google Books - Find it at Amazon
- 3. Stephanie Ryan, Michelle McNicholas, Stephen J. Eustace. Anatomy for Diagnostic Imaging. (2011) Page 124. ISBN: 9780702029714 - Google Books
- 4.Olivier P, Hayon-Sonsino D, Convard J, Laloë P, Fischler M. Measurement of Left Mainstem Bronchus Using Multiplane CT Reconstructions and Relationship Between Patient Characteristics or Tracheal Diameters and Left Bronchial Diameters. Chest. 2006;130(1):101-7. doi:10.1378/chest.130.1.101 - Pubmed