166 



Diaphragm. 



220. The Diaphragm, Diaphragma. Under Surface. 



The diaphragm consists of a muscular portion, Pars muscularis, and 

 a tendinous portion, Pars tendinea. 



The Pars muscularis is divided into the Pars himbalis, and the Pars costalis. 



The Pars lumlalis is formed by three pairs of crura. The i n n e r pair, 

 Crura interim, arises from the anterior surface of the third and fourth 

 lumbar vertebrae ; the crura cross once to form the aortic opening, 

 Hiatus aorticus, then a second time, whereby the o e s o p h a g e a 1 opening, 

 Foramen oesophageum, is formed. The m i d d 1 e pair of crura arises from 

 the lateral region of the second lumbar vertebra; the outer pair of 

 crura from the lateral region and the transverse processes of the first 

 lumbar vertebra. 



The Pars costalis arises from the six or seven lower ribs, the xiphoid 

 appendix (see Fig. 216) and the Liyammta arcuata Halleri. The Pars 

 muscularis is continued into the Pars tendinea seu Centrum tendineum (cen- 

 tral or cordiform tendon), which is shaped somewhat like a trefoil leaf, 

 and has in its right leaflet the quadrilateral Foramen vcnosum seu quadri- 

 laterum (opening for the Vena cava). 



