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ANATOMY AND PATHOLOGY 
Esophageal bra 
bronchoesoph 
Trachea 
Cranial bronch 
Ascending aor 
Right pulnnonary 
Right principal bro 
Right pulmonary 
phogus 
t subclavian a. 
vagus n. 
rachiocephalic trunk 
current laryngeal n. 
h of aorta 
Descending 
thoracic aorta 
ronchoesophageal a. 
L. pulmonary aa. 
L. principal bronchus 
Figure 3. — Trachea, bronchi and associated structures of the sheep. 
pulmonary artery and veins to the left principal 
bronchi in sheep and man. The left recurrent 
laryngeal nerve most commonly recurs around 
the aortic arch in most mammals and gives 
origin to caudal or inferior nerves, tracheal and 
esophageal branches and then ascends in the 
cervical region on the ventrolateral surface of 
the esophagus. 
Lung 
The nomenclature of the lung in quadrupeds 
and in man is based on division of bronchi 
rather than external fissures on the lung. All 
species except the horse and man have four 
lobes of the right lung. They are: the cranial 
lobe, middle lobe, caudal lobe, and accessory 
lobe. In all species, except horse and man, the 
cranial lobe of the left lung is divided into 
cranial and caudal parts by an interlobar fis- 
sure. In ruminants the right lung is also di- 
vided into cranial and caudal parts. The left 
lung, the smaller of the two lungs of sheep and 
calf, extends from the thoracic inlet caudally 
to the 11th intercostal space and the thymus 
