A bronchus, is a passage of airway in the respiratory system that conducts air into the lungs. The first bronchi to branch from the trachea are the right main bronchus and the left main bronchus. These are the widest and enter the lungs at each hilum, where they branch into narrower secondary bronchi known as lobar bronchi, and these branch into narrower tertiary bronchi known as segmental bronchi. Further divisions of the segmental bronchi are known as 4th order, 5th order, and 6th order segmental bronchi, or grouped together as subsegmental bronchi. The bronchi when too narrow to be supported by cartilage are known as bronchioles. No gas exchange takes place in the bronchi.
the secondary bronchi that branch off the primary bronchi are also called
lobar bronchi