After the macroscopic analysis, fragments of the trachea, tracheal bronchus, main and secondary bronchi
, and lungs were removed from the parietal and mediastinal surfaces in their cranial, middle and caudal regions.
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.
Each lobe is supplied by branched airways called the bronchial tree, which branches to form right and left primary bronchi that again divide into secondary bronchi