BODY CAVITIES, DIAPHRAGM AND MESENTERIES 



189 



The Omental Bursa or Lesser Peritoneal Sac. — According to Broman, the 

 omental bursa is represented in 3 mm. embryos by a peritoneal pocket which 

 extends cranially into the dorsal mesentery to the right of the esophagus. A 

 similar pocket present on the left side has disappeared in 4 mm. embryos. Lateral 

 to the opening of the primitive lesser peritoneal sac, a Kp-Uke fold of the mesentery 



Inferior vena cava 



luilciform ligament 



Coronary attachment of 

 liver to diaphragm 



Sup. recess of lesser 

 peritoneal sac 



Pleuro- 

 membrane 



Inferior vena cava 

 Plica vena, cava 



Mesonephric fold 

 Genital fold 



PI euro- peritoneal 



foramen 



Pleuro-peritoneal 



men 



Lesser omentum 



Greater omentum 



Spleen 



Stomach 



Lesser peritoneal sac 

 iorta 



Fig. 200. — A diagrammatic ventral view of the middle third of a human embryo 12 to 15 mm. long. 

 The figure shows the caudal surface of a section through the stomach and spleen, a ventral view of the 

 stomach, the liver having been cut away to leave the sectioned edges of the lesser omentum and plica 

 vena; cavae, and the caudal surface of the septum transversum and pleuro-peritoneal membrane. Upon 

 the surface of the septum is indicated diagrammaticaUy the attachment of the liver. (Based on figures 

 of Mall and F. T. Lewis and model by H. C. Tracy.) 



is continued caudally along the dorsal body wall into the mesonephric fold as the 

 plica vena cavce, in which the inferior vena cava later develops (Fig. 199). The 

 Kver, it will be remembered, grows out into the ventral mesentery from the fore- 

 gut, and, expanding laterally and ventrally, takes the form of a crescent. Its 

 right lobe comes into relation with the phca venae cavae, and, growing rapidly 

 caudad, forms with the plica a partition between the lesser sac and the peritoneal 



