A bronchus (plural bronchi, adjective bronchial) is a caliber of airway in the respiratory tract that conducts air into the lungs.
No gas exchange takes place in this part of the lungs.
In humans, the trachea (windpipe) divides into two main bronchi (also mainstem bronchi), the left and the right, at the level of the sternal angle.
The right main bronchus is wider, shorter, and more vertical than the left main bronchus.
The main bronchi subdivide into two and three secondary bronchi that each serve the left and right lungs, respectively.
The lobar bronchi divide into tertiary bronchi.
Each of the segmental bronchi supplies a bronchopulmonary segment.