470 



LABORATORY MANUAL OF HUMAN ANATOMY 



(d) Paraduodenal fossa (fossa paraduodenalis) (fossa of Landzert). 



This fossa is rarely found in the adult, occurring in a little less 

 than three per cent, of the cases. It is more frequently found in the 

 new-born. It is situated some distance to the left of the terminal 

 portion of the duodenum. If present, note especially its relation 

 to the inferior mesenteric vein and the ascending branch of the left 

 colic artery. The peritoneal folds raised by these vessels produce 

 the fossa. What is the plica mesentericomesocolica ? 



Intestinum jejunum 



FlG. 247. 



Mesocolon transversum 



V. xnesenterica inf. 



Plica duodenalis sup. 



Fossa duodenal is sup. 



Fossa duodenalis inf. 



Plica duodenalis inf. 



__ ^^^^ __ . colica sinistra 



Mesenterium 



Pars ascendens duodeni 



Fossae duodenales superior et inferior (after Jonnesco). (From Poirier et Charpy, Traite d'Anat. 

 hum., Paris, 1901, 2 ed., t. iv. p. 907, Fig. 483.) 



(e) Retroduodenal fossa (fossa retro duodenalis] . 



Infrequent in occurrence. Upon what does the formation of 

 this fossa depend? In this connection reference should again be 

 made to the fascia of Treitz. 



Many anatomists recognize the existence of but one fossa at this 

 angle. It is called the duodenojejunal fossa of Treitz. The stu- 

 dent should refer to Poirier et Charpy, t. iv. p. 269. 



Peritoneal Plicae and Fossae about the Caecum. 



Before proceeding to a study of these plicae and fossae, some 

 idea should be had concerning the disposition of the folds of 

 peritoneum forming the mesentery at the iliocaecal junction. 

 Arriving at this junction, the right leaf of the mesentery passes 

 from the anterior surface of the ileum upon the caecum, and 

 the left leaf takes a similar course posteriorly. They then rejoin 

 upon the external border and inferior extremity of the caecum 

 and the base of the appendix. In passing from the ileum to the 

 caecum and appendix, the folds of the mesentery meet the short 



