DEVELOPMENT OF THE PEEITONEUM. 



1253 



Stomach 



Median plane 



Caecum 



Duodem 



Cff'cum 



The 

 mesentery 



Mesentery obliterated 

 i 



Median plane 



Transverse mesocolon 



abdomen is, as it were, caught in behind the stomach and lesser omentum. This portion 



of the cavity becomes the upper part (vestibule) of the omental bursa, and at first it 



communicates with the general cavity by a wide opening to the right of the lesser 



omentum;* but the growth ' 



of the liver, encroaching 



upon the opening, and 



other causes, reduce it to 



a relatively small size, 



and it forms the foramen 



epiploicum in the adult. 



The greater omentum 

 is, as pointed out above, 

 a bag-like growth of the 

 lower part of the meso- 

 gastrium, which passes 

 downwards and to the left 

 in front of the transverse 

 colon. As shown in Fig. 

 975, A and B, it is first 



Rectum- 

 Mesentery of descending colon 



entirely unconnected with 

 the transverse colon and 

 mesocolon ; but about the 

 third or fourth month it 

 becomes united to both, 

 and the adult condition is 

 established (Fig. 975, C). 



The mesentery 



FIG. 974. Two DIAGRAMS TO ILLUSTRATE THE DEVELOPMENT OP THE 

 MESENTERIES. 



lu the first figure the rotation of the intestinal loop and the continuous 

 primitive mesentery is shown. In the second figure (to the right), 

 which shows a more advanced stage, the portions of the primitive 

 mesentery (going to the ascending and descending colons) which dis- 

 appear, through their adhesion to the posterior abdominal wall, are 

 shaded dark ; the portions which persist are lightly shaded. 



It would appear that 

 the growth of the inferior 

 part of the omental bursa, 



and of the greater omentum, is primarily due to a proliferation of the cells over a limited area 

 of the mesogastrium, and a resulting folding of this layer downwards and t.o the left. 



In the upper part of the mesogastrium the spleen is developed, and the portion of 

 this fold which intervenes between the stomach and spleen forms the gastro-lienal 



ligament, whilst the part 

 behind the spleen becomes 

 the lieno-renal ligament. 



Of the primitive mesentery, 

 the portion connected with the 

 stomach the mesogastrium 

 becomes modified in the 

 manner just described. The 

 next division the meso- 

 duodenum disappears com- 

 pletely, owing to the turning 

 over of the duodenal loop 



_ _\ /"\YI 4r\ I^-Q TMrvVi^- oirlo or-*/ 



on to its right side, and its 

 subsequent adhesion to the 

 posterior abdominal wall, ac- 

 companied by the absorption 

 of its mesentery. The mesen- 

 teries of the small and large 

 shows the beginning of the greater omentum and its independence of . . 



the transverse mesocolon fin B, the two come in contact ; and in %****** a ' C0nfc "?, UOUS at 



C, they have fused along the line of contact. (According to Lock- first (tig. 972). When the 

 wood, the two layers of the fold shown in A, running in between rotation of the intestinal loop 

 the greater omentum and transverse mesocolon, instead of fusing, as takes place around the superior 

 shown in B, are drawn out unfolded producing the condition mp( , pr frprir ar fprv / spp ahovp^ 

 shown in C.) A, stomach ; B, transverse colon ; C, small intestine ; mej ' ei 7 ^ Se< ' aDove ;> 



D, duodenum ; E, pancreas ; F, greater omentum ; G, placed in the beginning of the large 

 great sac ; H, in omental bursa. intestine, with its mesentery, 



is carried to the right across 



e duodenum, and a fan -shaped portion of the general mesentery, lying within the 



ncavity of the loop, is partially cut off; this, later on, forms the mesentery proper 



the adult. At first it is continuous by its right border with the mesentery of the 



Fia. 975. DIAGRAMS TO ILLUSTRATE THE DEVELOPMENT OF THE 

 . GREATER OMENTUM (after Hertwig). 



