Main bronchus

The main bronchus (Primary bronchus; Principal bronchus) is defined as one of the two primary branches of the trachea that arise at the carina and conduct air into each lung. The trachea bifurcates into the right main bronchus and the left main bronchus. Each main bronchus is the first airway segment after the trachea and serves as the principal conduit for airflow to the respective lung, subsequently dividing into lobar bronchi that supply individual lobes.

The right main bronchus is typically shorter, wider, and more vertical than the left, which is longer, narrower, and more horizontal due to the position of the heart and mediastinal structures.