DEVELOPMENT OF THE ALIMENTARY TUBE AND APPENDED ORGANS. 337 



The lesser curvature is connected with the ventral body wall by the -ventral 

 mesogastrium (Fig. 301). 



In further development, apart from histogenesis, the greater curvature 

 becomes much more prominent and the organ as a whole changes its position, 

 the latter process beginning in embryos of 12 to 14 mm. The cephalic (car- 

 diac) end moves toward the left side of the body, the pyloric end toward the 

 right At the same time the stomach rotates, the greater curvature turning 



Ventral mesogastrium 



Aorta 



Spleen 



Dorsal mesogastrium 

 ~ Cceliac artery 



Pancreas 



ms Sup. mesenteric artery 



Common mesentery 



SBr-- Inf. mesenteric artery 



.-/ 



"'" Hind-gut (rectum) 

 FIG. 301. Gastrointestinal tract and mesenteries of a human embryo of 6 weeks. Toldl. 



Caecum 



caudally from its dorsal position and the lesser curvature cranially from its 

 ventral position. The result is that the organ comes to lie in an approximately 

 transverse position in the body, with the cardiac end to the left, the pyloric end 

 to the right, the greater curvature directed caudally, and the lesser curvature 

 directed cranially (compare Figs. 285 and 301 with Figs. 314 and 342).* 



* These changes may be more easily understood if the student will hold a closed book in the 

 sagittal plane in front of him, with the back of the book toward, and the open edge away from him. 

 The back represents the greater curvature, the open edge the lesser curvature. The upper end of 

 the book represents the cardiac end of the stomach, the lower end the pylorus. Turn the upper 

 (cardiac) end to the left, the lower (pyloric) end to the right, at the same time allowing the back of 

 the book (the greater curvature) to drop downward on the side toward the body. The changes in 

 the position of the book represent the changes in the position of the developing stomach. 



