THE PERITONEUM 



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hepatic or lesser omentum, connecting the stomach with the liver; and (2) the falciform ligament, 

 connecting the liver with the ventral body wall. v 



The stomach undergoes a rotation on its longitudinal axis so that its anterior border^ 

 (lesser curvature) is turned to the right, and its posterior border (greater curvature) to the left 

 (fig. 901). Thus the posterior mesentery of the stomach [mesogastrium], bulges to the left and 

 forward, carrying with it the spleen and pancreas. The portion of the mesentery corresponding 

 to the pancreas, and that from the spleen to the root of the mesentery, become fused with the 

 posterior body wall. The portion of the primitive mesogastrium between the stomach and 

 spleen persists as the gastro-splenic omentum (or ligament), while the lower portion arches 

 forward and downward as an extensive fold, the great omentum. The portion of the peritoneal 

 cavity left behind the stomach is termed the bursa omentalis, or lesser sac, the remainder of 

 the peritoneal cavity being the greater sac. 



Along with the pancreas, the duodenum becomes adherent to the posterior wall. The 

 remainder of the intestine forms a loop (fig. 901), the upper portion of which forms the jejuno- 

 ileum, the lower portion the large intestine. The intestinal loop rotates counter-clockwise, 

 so that the caecum and ascending colon are carried over to the right side of the body cavity, 

 where (with the corresponding portion of the primitive mesentery) they become adherent to 

 the posterior body wall (fig. 901). The mesentery of the transverse colon persists (though 

 fused partly with the great omentum, as explained later under development). The descending 

 colon becomes displaced to the left side, and (together with its mesentery) becomes adherent 

 to the posterior wall of the abdomen. The mesentery of the sigmoid colon usually persists 

 (in part), while that of the rectum is obliterated. Through these modifications of the peri- 



FiG. 901. — Diagrams Illustrating the Development of the Great Omentum, Mesentery, 

 ETC. A, Earlier Stage; B, Later Stage. 

 bid, caecum; dd, small intestine; dg, yolk-stalk; di, colon; du, duodenum; gc, greater 

 curvature of the stomach; gg, bile duct; gn, mesogastrium; k, point where the loops of the 

 intestine cross; mc, mesocolon; md, rectum; mes, mesentery; wf, vermiform appendix. 

 (McMurrich after Hertwig.) 



md 



toneum, and through unequal growth in the different regions, the simple primitive intestinal 

 tube is transformed into the complicated adult canal. The details of the transformation will 

 be more fuUy discussed later. 



Under certain rare conditions, the developmental process is modified so as to produce a 

 situs inversus, which may be partial or complete, involving both thoracic and abdominal 

 viscera. Under these circumstances, the viscera are transposed, the right and left sides being 

 reversed. 



THE PERITONEUM 



The peritoneum, as has been shown, is a serous membrane which lines the cav- 

 ity of the abdomen from the diaphragm to the pelvic floor, and invests or covers to 

 a varying extent the viscera which that cavity contains. Viewed in its very sim- 

 plest condition, it may be regarded as a closed sac, the inner surface of which is 

 smooth, while the outer surface is rough and is attached to the tissues which sur- 

 round it. 



In the male subject the peritoneum forms actually a closed sac; but in the 

 female its wall exhibits two minute punctures, which correspond to the openings 

 of the Fallopian tubes. That part which lines the walls of the abdomen is termed 

 the parietal peritoneum; that which is reflected on to the viscera is the visceral 

 peritoneum. The disposition of the peritoneum may first be studied by noting 



