Macroscopic examination of specimens from infected chickens showed extensive hyperemia of the respiratory tract, followed by exudate and casts extending from the tracheal bifurcation to the secondary bronchi
These split into secondary bronchi
, which then subdivide into narrower, tertiary bronchi.
The primary bronchus branches into successively smaller bronchi; two secondary bronchi
supply air to each lobe of the two-lobed left lung and three secondary bronchi
serve the three-lobed right lung.