THE TRACHEA AND BRONCHI 



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The Right Bronchus (bronchus dexter}, wider, shorter, and more vertical in direc- 

 tion than the left, is about 2.5 cm. long, and enters the right lung nearly opposite 

 the fifth thoracic vertebra. The azygos vein arches over it from behind; and the 

 right pulmonary artery lies at first below and then in front of it. About 2 cm. 

 from its commencement it gives off a branch to the upper lobe of the right lung. 

 This is termed the eparterial branch of the bronchus, because it arises above the right 

 pulmonary artery. The bronchus now passes below the artery, and is known as the 

 hyparterial branch ; it divides into two branches for the middle and lower lobes. 



Fio. 961. Front view of cartilages of larynx, trachea, and bronchi. 



The Left Bronchus (bronchus sinister) is smaller in caliber but longer than the 

 right, being nearly 5 cm. long. It enters the root of the left lung opposite the sixth 

 thoracic vertebra. It passes beneath the aortic arch, crosses in front of the esoph- 

 agus, the thoracic duct, and the descending aorta, and has the left pulmonary 

 artery lying at first above, and then in front of it. The left bronchus has no 

 eparterial branch, and therefore it has been supposed by some that there is no 

 upper lobe to the left lung, but that the so-called upper lobe corresponds to the 

 middle lobe of the right lung. 





