310 CLINICAL APPLIED ANATOMY. 



deviation of the trachea to the right in the thorax, would 

 strike the left wall of the tube and rebound into the right 

 bronchus. The lung signs produced depend upon the point 

 of lodgment of the foreign body. The body, if small, may 

 slip past the bronchus of the upper lobe, and this is more 

 likely to occur on the right side owing to the greater size of 

 the main bronchus. Under such circumstances the upper lobe 

 will remain unaffected. 



The relation of the main or stem bronchi to the chest wall is 

 of some interest in connection with bronchiectasis. They 

 commence at the bifurcation of the trachea, and passing down- 

 wards and backwards, terminate for all practical purposes at the 

 level of the eighth ribs. The bifurcation of the trachea lies to 

 the right of the mid-line at the level of the disc between the 

 fourth and fifth dorsal vertebrae. This point corresponds in 

 level to the fourth dorsal spine posteriorly, and to the junction 

 of the second right costal cartilage with the sternum in front 

 (level of the sterno-manubrial joint). The stem bronchi become 

 so small as to be negligible at the level of the eighth ribs 

 posteriorly, the right two inches and the left three inches from 

 the spines of the vertebrae. Viewed from the front of the thorax, 

 these terminal points correspond to the right fifth rib in the 

 par asternal line, and the corresponding rib on the left side just 

 internal to the nipple line. 



In children, the trachea bifurcates opposite the third costal 

 cartilage in front and the terminations of the stem bronchi reach 

 the same ribs as in the adult, but at half the distance from the 

 vertebral spines. 



The points at which the branches to the upper lobes arise can 

 be found by measuring downwards along the lines of the stem 

 bronchi. The eparterial bronchus, which supplies the right 

 upper lobe, arises one inch below the bifurcation of the trachea, 

 whilst the bronchus to the left upper lobe is two inches below the 

 bifurcation. 



The middle lobe of the right lung is solely supplied by the first 

 right ventral hyparterial bronchus. 



