106 



(ESOPHAGUS, STOMACH, AND INTESTINES. 



stomach is known as mesogastrium and the parts attached to the future colon and 

 rectum are termed respectively mesocolon and mesorectum. The stomach begins to 

 assume its characteristic shape while still lying with its longitudinal axis in the 



Fig. 126. FRONT VIEW OF ALIMENTARY CANAL, RATHER LESS ADVANCED IN 



DEVELOPMENT THAN THAT SHOWN IN FIG. 125, D. (His.) ^ 



The pharynx and upper part of oesophagus, and termination of the large 

 intestine are not represented. Lettering as in fig. 125. 



median plane of the body ; it is then seen that the mesogastrium 

 passes to its greater curvature (fig. 127), which, therefore, is 

 that corresponding to the mesenteric border of the intestine. 

 And as the pyloric extremity of the stomach and lesser curva- 

 ture are tilted forwards and upwards, and at the same time 

 the whole organ turns over on ,its right side, the mesogastrium 

 becomes proportionally lengthened to permit of this change of 

 position, and the right surface of the stomach (now posterior) 

 rests against the anterior surface of what was previously 

 the right side of the mesogastrium, the mesogastrium thus 

 coming to form the posterior boundary of the omental sac (fig. 

 128). From near its attachment to the stomach a free fold 

 subsequently grows over the intestines, and becomes the great 

 omentum. 



The gastro-hepatic omentum is formed by the gradual thinning of a mass of 

 mesoblastic tissue which from the first connects the ventral wall of the stomach with 

 the anterior wall of the abdomen, and within which the hypoblastic outgrowth 



Fig 127 DIAGRAM OF THE MESENTERY, STOMACH AND INTESTINE OF A HUMAN EMBRYO OF six 



WEEKS. (Toldt.) 



st, stomach; g.c, greater curvature; Lc, smaller curvature; mg, mesogastrium ; spl, spleen; 

 p, pancreas ; c. caecum ; r, rectum ; me, mesentery ; ao, aorta ; d, cceliac axis ; s.mes.a, i.mes.a, supe- 

 rior and inferior mesenteric arteries. 



Fie 128 DIAGRAM OF A SECTION ACROSS THE ABDOMEN OF A HUMAN EMBRYO OF THE THIRD 



MONTH. (Toldt.) 



I, I, liver ; k, kidneys ; g.o, great omentum ; /.o', omental sac ; s.o, small omentum. (The dotted 

 line has not been carried quite far enough.) The other letters as in fig. 127. 



which forms the liver becomes developed. The part of this mesoblastic connexion 

 which lies between the liver and stomach becomes the gastro-hepatic or lesser 

 omentum, and its free border which was at first directed downwards (caudal wards) 

 becomes with the descent of the stomach directed anteriorly (ventrally), and eventu- 

 ally with the turning of that organ laterally it also is directed towards the right, and 

 thus comes to form the anterior boundary of the entrance into the omental sac. 



