936 



A MANUAL OF ANATOMY 



Continuity and Reflections of the Pleura. — (i) In the transverse 

 direction. — Commencing at the deep surface of the sternum, the 

 parietal pleura of each side passes backwards to the pericardium, 

 the two being in contact except for a little inferiorly. They form 

 the lateral boundaries of the space which is called the anterior 

 mediastinum. When they reach the pericardium the two pleurae 

 separate, each keeping to its own side of that sac, and so forming the 

 pericardial pleura, which bounds laterally the space known as the 

 middle mediastinum. Each pleura in this manner reaches the 

 anterior aspect of the root of the corresponding lung, where it 

 becomes the visceral pleura. This covers the front of the root of the 

 lung, and then invests the entire organ, dipping into its fissure or 

 fissures, as the case may be, and giving a covering to the posterior 



Fig. 



383. — Diagram showing the Reflections of the Pleura 

 (Transverse Section). 



aspect of the root. On leaving the back of the root of each lung, the 

 two pleurae pass backwards, slightly over the pericardium, trachea, 

 and oesophagus, and over the descending thoracic aorta, to the lateral 

 aspects of the bodies of the thoracic vertebrae. These portions form 

 the lateral boundaries of the space which is called the posterior 

 mediastinum. From the vertebral column each pleura passes out- 

 wards over the gangliated cord of the sympathetic, and then lines 

 the inner surfaces of the ribs, as well as the internal intercostal 

 muscles. In this manner it reaches the deep surface of the 

 sternum. 



From the foregoing description it will be evident that the pleura, 

 in passing from the deep surface of the sternum to the vertebral 

 column, meets with, and is reflected over, the lung and its root 



