98 THORAX 



Relations of the Extra- pulmonary Part of the Right 

 Bronchus. The right bronchus is much more vertical than 

 the left (Fig. 48), and, as the ridge which separates the orifices 

 of the two bronchi at their origins, lies to the left of the 

 median line of the trachea, the right bronchus is the 

 direct continuation of the .trachea, and foreign bodies, which 

 have entered the windpipe, pass more frequently into it than 

 into the left bronchus. It passes downwards and laterally 

 from the upper border of the fifth thoracic vertebra to the 

 level of the upper part of the sixth thoracic vertebra, where 

 it enters the hilus. Anterior to the extra-pulmonary part of 

 the right bronchus are the ascending part of the aorta, the 

 lower part of the superior vena cava, and the right pulmonary 

 artery. Above it is the arch of the azygos vein ; 2xi& posterior to 

 it are the azygos vein, the posterior pulmonary plexus, and the 

 right bronchial artery. This part of the right bronchus gives 

 off one branch, which arises close to the hilus and is called 

 the eparterial bronchus, because it originates immediately 

 above the point where the right pulmonary artery crosses 

 anterior to the stem bronchus. 



Relations of the Extra-pulmonary Part of the Left Bronchus. 

 The extra-pulmonary part of the left bronchus commences 

 and ends at the same level as the corresponding part of the 

 right bronchus, but it has further to go, because the hilus of 

 the left lung is further from the median plane than the 

 hilus of the right lung ; therefore it is longer and less vertical 

 than the right bronchus. It gives off no branches. 



Anterior to it are the left pulmonary artery, and the upper 

 and left part of the pericardial sac which separates the 

 bronchus from the left auricle. Above it is the arch of the 

 aorta, and posterior to it are the descending aorta, the posterior 

 pulmonary plexus, the left bronchial arteries, and the oeso- 

 phagus. 



Dissection. The intra-pulmonary parts of the bronchi and the intra- 

 pulmonary parts of the pulmonary arteries and veins should now be 

 dissected. The dissectors must commence at the hilus of the lung and 

 follow the bronchus and the vessels into the interior of the lung, cutting 

 away the lung substance, but avoiding injury to the main branches of the 

 bronchus and of the artery, and the main tributaries of the veins. 



Relations of the Intra-pulmonary Parts of the Bronchi, the Pul- 

 monary Arteries and the Pulmonary Veins. After passing through the 

 hilus each bronchus descends, in the substance of the lung, to the lower end 

 of the lung, lying nearer the medial than the lateral surface, and nearer the 

 posterior than the anterior border. As it descends it gives off two sets of 



