BODY CAVITIES, DIAPHRAGM AND MESENTERIES 



199 



third pleural cavity. It lies to the right of the esophagus in the mediastinum and its average 

 diameter in the adult is 10 mm. 



When the stomach changes its position and form so that its mid-ventral 

 line becomes the lesser curvature and lies to the right, the position of the lesser 

 omentum is also shifted. From its primitive location in a median sagittal plane 

 with its free edge directed caudally it is rotated through 90 until it lies in a cor- 

 onal plane with its free margin facing to the right. The epiploic foramen now 



Supra 

 renal 

 fftand 



Lester _ 

 peritoneal 

 sac 



Duo- 



Vttllline 



vein 



Intestinal- 

 loop 



Mesonephros 

 Greater omentum 

 Stomach 



Left umbilical Vein 



Fig. 194. — An obliquely transverse section through a 10 mm. embryo at the level of the epiploic foramen 



(of Winslow). X 33. 



forms a slit-like opening leading from the peritoneal cavity into the vestibule 

 of the omental bursa. The foramen is bounded ventrally by the edge of the 

 lesser omentum, dorsally by the inferior vena cava, cranially by the caudate pro- 

 cess of the liver and caudally by the wall of the duodenum. 



During fetal life the greater omentum grows rapidly to the left and caudad 

 in the form of a sac flattened dorso-ventrally. It overlies the intestines ven- 

 trally and contains the inferior recess of the omental bursa (Fig. 195). The dor- 

 sal wall of the sac during the third and fourth months usually fuses with the trans- 

 verse colon where it overlies the latter. Caudal to this attachment, the walls 



