1106 



SPLANCHNOLOGY 



mesogastria are now directed backward, and the left forward. In this way a pouch, 

 the bursa omentalis, is formed behind the stomach, and this increases in size as 

 the digestive tube undergoes further development; the entrance to the pouch 

 constitutes the future foramen epiploicum or foramen of Winslow. The duodenum 

 is developed from that part of the tube which immediately succeeds the stomach; 

 it undergoes little elongation, being more or less fixed in position by the liver and 

 pancreas, which arise as diverticula from it. The duodenum is at first suspended 

 by a mesentery, and projects forward in the form of a loop. The loop and its mes- 

 entery are subsequently displaced by the transverse colon, so that the right surface 

 of the duodenal mesentery is directed backward, and, adhering to the parietal 

 peritoneum, is lost. The remainder of the digestive tube becomes greatly elongated, 

 and as a consequence the tube is coiled on itself, and this elongation demands a 

 corresponding increase in the width of the intestinal attachment of the mesentery, 

 which becomes folded. 



Aorta 



Ventral mesogastrium 



Spleen 



Dorsal 

 mesogastrium 



Celiac artery 

 Pancreas 



Superior mesenteric 

 artery 



Inferior mesenteric artery 



Hind-gut 



FIG. 985. Abdominal part of digestive tube and its attachment to the primitive or common mesentery. 



embryo of six weeks. (After Toldt.) 



Human 



At this stage the small and large intestines are attached to the vertebral column 

 by a common mesentery, the coils of the small intestine falling to the right of the 

 middle line, while the large intestine lies on the left side. 1 



The gut is now rotated upon itself, so that the large intestine is carried over in 

 front of the small intestine, and the cecum is placed immediately below the liver; 

 about the sixth month the cecum descends into the right iliac fossa, and the large 

 intestine forms an arch consisting of the ascending, transverse, and descending 

 portions of the colon the transverse portion crossing in front of the duodenum 

 and lying just below the greater curvature of the stomach; within this arch the 

 coils of the small intestine are disposed (Fig. 988). Sometimes the downward 



1 Sometimes this condition persists throughout life, and it is then found that the duodenum does not cross from the 

 right to the left side of the vertebral column, but lies entirely on the right side of the median plane, where it is continued 

 into the jejunum; the arteries to the small intestine (aa. intestinales) also arise from the right instead of the left side 

 of the superior mesenteric artery. 



