IQO 



THE ENTODERMAL CANAL AND THE BODY CAVITIES 



cavity. Thus the cavity of the lesser peritoneal sac is extended caudally from 

 a point opposite the bifurcation of the lungs to the level of the pyloric end of the 

 stomach. In 5 to 10 mm. embryos it is crescent-shaped in cross-section (cf. Fig. 

 Ill) and is bounded mesially by the greater omentum (dorsal mesentery) and the 

 right wall of the stomach, laterally by the liver and plica venae cavas, and ven- 

 trally by the lesser omentum (ventral mesentery). It communicates to the 

 right with the peritoneal cavity through an opening between the liver ventrally 

 and the pKca venae cavas dorsally (Fig. 201). This opening is the epiploic fora- 



Suprarenal gland- 



Liver 

 Lesser peritoneal sae 

 Duodenum 



Vitelline vnn 

 Intestinal loop. 



Mesonephros 

 Greater omentum 

 Stomoih 



eal vein 



Fig. 201.— An obliquely transverse section through a 10 mm. human embryo at the level of the epiploic 



foramen (of Winslow). X 33. 



men (of Winslow). When the dorsal wall of the stomach rotates to the left the 

 greater omentum is carried with it to the left of its dorsal attachment. Its tissue 

 grows actively to the left and caudally and gives the omentum an appearance of 

 being folded on itself between the stomach and the dorsal body wall (Fig. 200). 

 The cavity of the lesser peritoneal sac is carried out between the folds of the 

 greater omentum as the inferior recess of the omental bursa. 



From the cranial end of the sac there is constricted off a small closed cavity which is 

 frequently persistent in the adult. This is the bursa infracardiaca and may be regarded as a 

 third pleural cavity. It hes at the right of the esophagus in the mediastinum. 



