26 THORAX 



Contents of the Mediastinum and the Structures of the 

 Posterior Wall of the Thorax seen from the Right Side. 

 After the pleura has been removed from the right side of the 

 thorax and the extra-pleural tissue has been dissected away, 

 the following structures are exposed. Below and anterior to 

 the root of the lung is the pericardium. Entering the peri- 

 cardium below and posteriorly is the thoracic part of the inferior 

 vena cava, and entering the upper part is the superior vena 

 cava. The upper end of the superior vena cava is continuous 

 with the right innominate vein, which lies posterior to the 

 sternal end of the first costal cartilage. Arching over the root 

 of the lung, to join the superior vena cava, is the terminal part 

 of the azygos vein. Above the azygos vein and posterior to 

 the superior vena cava are parts of the trachea, the right vagus 

 nerve, and the oesophagus. On the posterior surface of the 

 root of the lung is the posterior pulmonary plexus, formed by 

 the vagus nerve, and posterior to the lung root is the vena 

 azygos. At a lower level, posterior to the pericardium, the 

 right margin of the oesophagus will be found anterior to the 

 vena azygos. Lateral to the vena azygos, on the sides of the 

 bodies of the vertebrae, lie the right aortic intercostal arteries, 

 the accompanying veins, and the splanchnic nerves. Still 

 more laterally, on the line of the heads of the ribs, runs the 

 sympathetic trunk, and beyond the sympathetic trunk are the 

 intercostal spaces and their contents. 



After the various parts mentioned above have been located 

 and defined, the dissectors should thoroughly clean the 

 sympathetic trunk and its branches and communications. 

 In the upper part of the thorax the trunk runs along the 

 heads of the ribs, but in the lower part it attains a more 

 anterior position. 



The Thoracic Portion of the Sympathetic Trunk. This is 

 continuous above with the cervical portion and below with 

 the abdominal portion. It has the appearance of a knotted 

 cord. The knots are ganglia, which consist of nerve cells and 

 fibres. The intermediate parts of the trunk consist of nerve 

 fibres alone. There are usually eleven ganglia, and, as 

 a rule, each ganglion lies opposite the head of a rib, but 

 the first is opposite the medial end of the first intercostal 

 space, or anterior to the neck of the first rib, and, as the 

 trunk inclines anteriorly below, one or two of the lower 

 ganglia lie on the bodies of the lower thoracic vertebrae. 



