322 CLINICAL APPLIED ANATOMY. 



which, when diseased, may give rise to secondary pleurisy, are 

 the aorta, the oesophagus and the mediastinal lymphatic glands. 

 The transverse and descending portions of the thoracic aorta are 

 in relation with the left pleural sac, and adhesive inflammation 

 may accompany aneurysms of these parts of the vessel. The 

 ascending aorta lies in relation with both sacs. The oesophagus 

 in the posterior mediastinum abuts upon the right pleural cavity, 

 which actually forms a small cul-de-sac between it and the spine. 

 Above and below the oesophagus is in relation with the left 

 pleural sac. 



The diaphragmatic pleura has intimate relations with the 

 peritoneum by lymphatic vessels which traverse the diaphragm. 

 These channels are tortuous and narrow, so the diaphragm to a 

 certain extent forms a barrier between the two serous sacs. 

 Tuberculous, septic or malignant disease may invade the pleura 

 by this route. Invasion may be facilitated by the occurrence of 

 a defect in the posterior part of the diaphragm below the external 

 arcuate ligament, in the region of the kidney. A small gap is 

 not uncommon in this situation, especially on the right side. 

 The fused subperitoneal and subpleural planes of connective 

 tissue then form the only barrier between the peritoneum and 

 the pleura. The base of the right pleura may be invaded directly 

 by abscesses, hydatids or malignant growths of the liver, the 

 diaphragm being perforated. The base of the left sac is separated 

 by the diaphragm from the left lobe of the liver, the fundus of 

 the stomach, the spleen and, when the stomach is contracted, 

 the transverse colon near its splenic flexure. Consequently the 

 left pleura can be invaded from any of these structures. The 

 upper poles of the kidneys lie upon the lower sinuses of the 

 pleura, the diaphragm intervening, so that perinephritic abscesses 

 may infect the pleural sacs. 



The costal pleura may be perforated by wounds of the chest or 

 the ends of fractured ribs. It may also be invaded by tuber- 

 culous and other inflammations of the ribs or chest walls, and 

 over-lying growths. Axillary abscesses occasionally give rise to 

 pleurisy, and this may be explained by the fact that the axillary 



