1266 



THE ORGANS OF DIGESTION 



These recesses or fossae may be divided into three groups viz. : (1) the duodenal 

 fossae; (2) pericecal fossae; and (3) the intersigmoid fossa. 



1. Duodenal Folds and Fossae. Moynihan has described no less than nine fossae 

 as occurring in the neighborhood of the duodenum. Three of these are fairly 

 constant. Five of the fossae are here considered: (a) The inferior duodenal 

 fossa or fossa of Treitz (Fig. 989) is the most constant of all the peritoneal fossae 

 in this region, being present in from 70 to 75 per cent, of cases. It is situated 

 opposite the third lumbar vertebra on the left side of the ascending portion of the 

 duodenum. Its opening is directed upward, and is bounded by a thin, sharp 

 fold of peritoneum with a concave free upper margin, called the inferior duodenal 

 fold (plica duodenomesocolica). The tip of the index finger introduced into the 

 fossa under the fold passes some little distance behind the ascending or fourth 

 portion of the duodenum. (6) The superior duodenal fossa (Fig. 989) is the next 

 most constant pouch or recess, being present in from 40 to 50 per cent, of cases. 



DUODENUM 



RIGHT DUODENO- 



MESOCOLIC 

 LIGAMENT 



INFERIOR 



MESENTERIC 



VEIN 



LEFT DUODE- 



NOMESOCOLIC 



LIGAMENT 



LEFT COLIC 

 ARTERY 



INFERIOR MESEN- 

 TERIC ARTERY 



FIG. 990. Duodenojejunal fossa. (Poirier and Charpy.) 



It often coexists with the inferior one, and its orifice looks downward, in the oppo- 

 site direction to the preceding fossa. It lies to the left of the ascending portion 

 of the duodenum. It is bounded by the free edge of the superior duodenal fold 

 (plica duodenojejunalis), which presents a semilunar margin; to the right it is 

 blended with the peritoneum covering the ascending duodenum, and to the left 

 with the peritoneum covering the perirenal tissues. The fossa is bounded in 

 front by the superior duodenal fold; behind by the second lumbar vertebra; to 

 the right by the duodenum, (c) The duodenojejunal fossa or mesocolic fossa 

 (recessus duodenojejunalis) is formed where the duodenojejunal angle enters the 

 root of the transverse mesocolon. There are two forms: (1) a single fossa and (2) 

 a double fossa. It can be seen by pulling the jejunum downward and to the right 

 after the transverse colon has been pulled upward. It will appear as an almost 

 circular opening, looking downward and to the right, and bounded by two free 

 borders or folds of peritoneum, the duodenomesocolic ligaments. The opening 



