Ioa> A MANUAL OF ANATOMY 



two bronchi, with the intervention of the deep cardiac plexus of 

 nerves. Posterior. — ^The oesophagus, which inclines partially to 

 the left of the trachea. Right. — ^The right pneumogastric nerve ; 

 the innominate artery, after it has left the front of the trachea ; 

 and the right pleural sac. Left. — ^The arch of the aorta and the 

 left common carotid artery, after these have left the front of the 

 trachea ; the left subclavian artery ; and the left recurrent laryngeal 

 nerve. 



Bronchi.— The bronchi, right and left, commence at the bifurca- 

 tion of the trachea, and each passes to the hilum of the correspond- 

 ing lung, where its ramifications commence. As in the trachea, 

 each bronchus is cylindrical and firm in front and at the sides, 

 but posteriorly it is flattened and membranous. There being 

 certain differences between the bronchi, a separate description is 

 required for each. 



The right bronchus is about i inch in length up to the point 

 where it gives off its first, or eparterial, branch. It has about six 

 cartilaginous rings, and is larger than the left bronchus. It is 

 more vertical than the left bronchus, and therefore coincides 

 with the direction of the trachea to a greater extent than its 

 fellow. 



Relations — Superior. — ^The right azygos vein arches over it to 

 open into the superior vena cava. Posterior. — ^The right pneumo- 

 gastric nerve. Inferior. — ^The right pulmonary artery, which sub- 

 sequently lies anterior to it. 



About I inch from its commencement the right bronchus gives 

 off a branch from its outer side which passes to the upper lobe of 

 the right lung. This branch is known as the eparterial bronchus, 

 because it arises above the right pulmonary artery. The rest of 

 the right bronchus is spoken of as being hyparterial. 



The left bronchus is about 2 inches in length. It has about 

 twelve cartilaginous rings, and is smaller than the right bronchus 

 on account of the smaller size of the left lung. Its course is more 

 oblique than that of its fellow, and it is directed downwards and 

 outwards beneath the arch of the aorta to the hilum of the left 

 lung. 



Relations — Anterior.— The. left pulmonary artery, which subse- 

 quently lies above it. Posterior. — The oesophagus and the descend- 

 ing thoracic aorta. 



The left bronchus has no eparterial branch. 



When the interior of the trachea is viewed from above, as in 

 using the laryngoscope, the openings of the two bronchi are seen 

 to be separated by a ridge which is situated to the left of the median 

 line, and more of the interior of the right bronchus than of the left 

 is visible. Partly on this account, and partly by reason of the 

 more vertical direction of the right bronchus, as well as its larger 

 size, a foreign body getting into the trachea is more apt to descend 

 into the right bronchus than into the left. 



