THE DIGESTIVE APPARATUS 



1107 



progress of the cecum is arrested, so that in the adult it may be found lying imme- 

 diately below the liver instead of in the right iliac region. 



Further changes take place in the bursa omentalis and in the common mesentery, 

 and give rise to the peritoneal relations seen in the adult. The bursa omentalis, 

 which at first reaches only as far as the greater curvature of the stomach, grows 

 downward to form the greater omentum, and this downward extension lies in front 

 of the transverse colon and the coils of the small intestine (Fig. 989) . Above, before 

 the pleuro-peritoneal opening is closed, the bursa omentalis sends up a diverticulum 



8th cervical nerve 



1st thoracic 

 vertebra 



Lung 



Stomach 

 12th thoracic 



nerve 

 Mesonephros 



Kidney 



5th lumbar 

 nerve, 



Ureter 

 Cecum intestine Wolffian duct 



FIG. 986. Reconstruction of a human embryo of 17 mm. 



(After Mall.) 



on either side of the esophagus; the left diverticulum soon disappears, but the right 

 is constricted off and persists in most adults as a small sac lying within the thorax 

 on the right side of the lower end of the esophagus. The anterior layer of the 

 transverse mesocolon is at first distinct from the posterior layer of the greater 

 omentum, but ultimately the two blend, and hence the greater omentum appears as 

 if attached to the transverse colon (Fig. 990) . The mesenteries of the ascending and 

 descending parts of the colon disappear in the majority of cases, while that of the 

 small intestine assumes the oblique attachment characteristic of its adult condition. 

 The lesser omentum is formed, as indicated above, by a thinning of the meso- 

 derm or ventral mesogastrium, which attaches the stomach and duodenum to the 

 anterior abdominal wall. By the subsequent growth of the liver this leaf of 

 mesoderm is divided into two parts, viz., the lesser omentum between the stomach 



