THE PLEURA 



451 



placed more on the left side; consequently the right pleural cavity and lung are 

 larger than the left. Practically all the organs in the thorax are in the mediastinal 

 space with the exception of the lungs, the posterior vena cava, and the right phrenic 

 nerve. The part in which the heart and the pericardium are situated, together 

 with that above it, is usually called the middle mediastinal space; the parts before 

 and behind this are termed the anterior and posterior mediastinal spaces respec- 

 tively. 



THE PLEURA 

 The pleurae are two serous sacs which line the pleural cavities and are reflected 

 at the roots of the lungs to invest those organs. We, therefore, distinguish parietal 

 and visceral parts of the pleura. 



LUjamcnluin nucha: 



Scaptdn 

 Spinal cord 



Disc between third 



and fourth thoracic 



vcrtebrie 



Thoracic duct 



Third rib 



Left vagus nerve 



Left phrenic nerve 



Costal pleura 



Mediastinal 

 pleura 



Second costal 

 cartilage 



Internal thoracic 



vessels 



Sternum 



Sympathetic nerve 

 — Subcostal vessels 



(Esophagus 

 Right vagus nerve 



Anterior vena cava 



Right phrenic 

 nerve 



Pulmonary pleura 

 J Costal pleura 



Brachial vessels 

 Humerus 



in,. :;.)S. — ( 'idiss-sKfTiON OF Thorax cik .\i.\\-i:ohn Ihai.. 

 Tr., Trachea; S, left brachial artery; B, brachiocephalic artery; t.g., lymph gland. Pleura indicated by red 



line. 



The parietal pleura (Pleura parietalis) lines the cavity in which each lung is 

 situated (Cavum pleurae). On the lateral thoracic wall it is adherent to the ribs 

 and intercostal muscles and is termed the costal pleura (Pleura costalis). Behind 

 it is closely attached to the diaphragm, forming the diaphragmatic pleura (Pleura 

 diaphragmatica). The part which is in apposition with the opposite sac or covers 

 the mediastinal organs is termed the mediastinal pleura (Pleura mediastinalis) ; 



