278 



HUMAN EMBRYOLOGY AND MORPHOLOGY. 



post-arterial part. It forms the mesentery of the ascending and ■» 

 transverse colon and also the lower part of the mesentery of the . 

 small bowel. 



jejunum- 



colon 



ileo-col. art. 

 ■mesentery 

 rtery of appendix 



appendix 

 ~post aspzct.) 



'leum 

 uit. intest. canal 



A. 



aso. meso-col.fi 



retro-caec. 

 bloodless 



ileo-col. 

 fossa 



ileum 



caec. fossa 

 mesent 



appendix 



B. 



Fig. 225 A. —The Appendix and Peritoneal Folds at the end of the 2nd month of 



foetal life. The Intestinal Loop is viewed from the left side. 

 Fig. 225 B. — Peritoneal Fossae in the lleo-caecal Region. 



At the seventh week the great growth of the anterior limb, to 

 form the coils of the jejunum and ileum, causes the U-shaped 

 loop to rotate so that the splenic flexure of the colon comes 

 against the spleen. This brings the transverse meso-colon, con- 

 taining the middle colic artery, against the part of the meso- 

 gastrium which forms the great omentum (Fig. 226). These two 

 layers adhere. The rotation places that part of the loop mesentery, 

 which forms the ascending meso-colon, against the duodenum, 

 and at the same time the duodenal loop is pressed into its 



