Dorsobronchus

The fifth dorsobronchus turns posteriorly at the point where it approximates the dorsolateral margin of the lung and extends toward the posterior tip of the mesobronchus.

Source: wiktionary

The ventral end of the mesobronchus branches into several ventrobronchi, and the caudal end of the mesobronchus branches into several dorsobronchi.

Source: wiktionary

As air enters the avian lung through a primary bronchus, it flows caudad to the first abdominal air sac (E) and then through the large laterobronchus (5) to the posterior thoracic air sac (D). Reversal of pressure in the posterior thoracic and abdominal air sacs forces air up and forward through the primary bronchus (2) and each dorsobronchus (4) through the paleopulmo through parabronchi (6) to the ventrobronchi (3). Simultaneously, low pressure in the anterior sacs (cervical, interclavicular and anterior throacic) supports the flow from the ventrobronchi; prior to exhalation this air enters the anterior air sacs. Increased pressure in the anterior air sacs forces exploited air out the tracheal system.

Source: wiktionary

In the song birds, the primary bronchus has become so narrow after branching of the last dorsobronchus that it cannot be distinguished from a parabronchus.

Source: wiktionary