1086 



THE EESPIEATOEY SYSTEM. 



pleural reflection; whilst inferiorly it becomes continuous with the diaphrag- 

 matic pleura, of its own side, at the base of the pericardium. 



Above the root of the lung the mediastinal pleura passes directly from the 

 sternum to the vertebral column. In that region the left mediastinal pleura 

 is applied to the arch of the aorta and the phrenic and vagus nerves ; to the left 

 innominate vein, the left superior intercostal vein and the left common carotid and 



left subclavian arteries ; to the 

 oesophagus and the thoracic duct. 

 The right mediastinal pleura, on 

 the other hand, is applied, above 

 the root of the lung, to the superior 

 part of the vena cava superior and 

 the right innominate vein ; to the 

 innominate artery; to the vena 

 azygos, as it hooks forwards above 

 the bronchus; to the vagus and 

 phrenic nerves ; and to the right 

 side of the trachea. 



Opposite the root of the lung, 

 as well as in the region below 

 it, the mediastinal pleura clothes 

 the corresponding aspect of the 

 pericardium (pleura pericardiaca), 

 and is somewhat firmly attached 

 to it. As the phrenic nerve passes 

 downwards upon the pericardium 

 it likewise is covered over by the 

 pleura. In the region correspond- 

 ing to the superior part of the 

 lateral aspect of the pericardium 

 the mediastinal pleura is prolonged 

 laterally, so as to form an invest- 

 ment for the root of the lung, and 

 becomes continuous around the 

 hilum of the lung with the pul- 

 monary pleura. Below the root 

 of the lung the two layers of pleura 

 which invest it come into apposi- 

 tion with each other, and are pro- 

 longed downwards as a distinct 

 fold, termed the ligamentmn pul- 

 monale. This fold stretches be- 

 tween the pericardium and the 

 inferior part of the mediastim" 

 surface of the lung, and ends in- 

 feriorly in a free border. 



Dorsal to the root of the lu] 



FIG. 864. LATERAL VIEW OF THE EIGHT PLEURAL SAC IN an d the ligamentum pulmonJ 



the mediastinal pleura on the 

 right side passes over the oesophagi 

 to the vertebral column, whilst 01 

 the left side it passes dorsally over the thoracic aorta, and to a small extent ove 

 the lower end of the oesophagus, in the region immediately adjoining the dij 

 phragm and ventral to the thoracic aorta. 



Lines Of Pleural Reflection. These are three in number viz., the sternal, 

 vertebral, and the diaphragmatic. The pleural cavities are not symmetrical. The left 

 longer and narrower than the right, and it thus happens that the lines of pleural refit 

 tion do not accurately correspond on the two sides of the body. Further, although th 



A SUBJECT HARDENED BY FORMALIN INJECTION. The 

 blue lines indicate the outline of the right lung, and also 



the position of its fissures. 



