9 6 



THORAX 



tube kept constantly patent by a series of cartilaginous rings 

 embedded in its walls. Posteriorly the rings are deficient 

 and in consequence the tube is flattened behind (Fig. 43). 

 It enters the thorax at the upper aperture, posterior to the 

 upper border of the manubrium, and it terminates, at the level 

 of the lower border of the manubrium and the upper border 

 of the fifth thoracic vertebra, by dividing into a right and a 

 left bronchus. It lies, therefore, in the superior mediastinum, 



Trachea 



Left bronchus 



FIG. 48. Drawing of a Stereoscopic Skiagraph of the Trachea and Bronchi 

 injected with starch and red lead. 



and its median axis is in the median plane, except at the 

 lower end where it deviates slightly to the right. 



Relations. Posteriorly, it is in contact with the oesophagus, 

 which separates it from the vertebral column ; and in the 

 angle between its left border and the anterior surface of 

 the oesophagus is the left recurrent nerve (Fig. 43). 



Anteriorly, it is in relation below with the arch of the 

 aorta, the deep part of the cardiac plexus intervening ; and 

 at a higher level with the innominate and left common 

 carotid arteries, the left innominate vein and the inferior 

 thyreoid veins. More superficially lie the remains of the 



