996 



THE ORGANS OF DIGESTION. 



jejuna! angle should penetrate the root of the transverse mesocolon. This occurs 



in two forms : (1) a single simple fossa (Fig. 619), and (2) a double fossa. Below 



the duodenum is the inferior mesenteric 

 artery, giving off the colica sinistra ; 

 passing over the fossa is the inferior 

 mesenteric vein. This was originally 

 described by Huschke in 1844. In 

 drawing the jejunum forward and to the 

 right, the mesocolon being raised, the 

 duodeno-mesocolic ligaments are seen 

 stretched between the duodeno-jejunal 

 angle and mesocolon. They seem to be 

 layers of mesentery passing into the 

 mesocolon. Limited by these folds and 

 by the upper surface of the duodeno- 

 jejunal angle and the inferior mesenteric 

 vein there appears an almost circular 

 opening leading into a deep fossa. This 

 plunges into the mesocolon and occupies 

 a retro-peritoneal space to the left of the 

 second lumbar vertebra, limited above by 

 the pancreas, on the right by the aorta, 

 and on the left by the left kidney. In 



this cavity is the angle of the duodeno-jejunal flexure and higher up can be seen 



under it the left renal vein. The orifice admits the little finger and its depth is 



2 or 3 cm. 



The inferior mesenteric vein passes at first along the adherent mesocolic 



border of the left fold and then its concavity crosses near the orifice. 



Jonnesco has seen one case of a double duodeno-jejunal fossa where there were 



three ligaments. All these are related to the inferior mesenteric vein. 



It is not believed that any of these are pathological. They are more or less 



developed in children and new-born. 



FIG. 619. Simple duodeno-jejunal fossa. (Jonnesco.) 



Classification. 



I. Duodenal fossae (may co- 

 exist). 



( Inferior 

 ( Superior 



II. Duodeno-jejunal or meso- ^ Q. -, 



colic fossa (never coexists with > ^ 



,, j- \ I Double 



the preceding). 



Non-vascular most often. If vas- 

 cular, is the fossa of Treitz. 



Always vascular, simple 

 venous. 



Always vascular, venous. 



Fossa Intersigmoidea. 



Under the name intersigmoid or subsigmoid fossa, Treitz described a funnel- 

 shaped recess of the peritoneum, commonly found in the foetus, next most often 

 in the child, and rather rarely in the adult. Its mouth opens below in the left 

 iliac fossa on the left side of the root of the mesentery of the sigmoid flexure. 

 To find it, turn the flexure over to the right (Fig. 620). 



The opening usually lies upon the left external iliac vessels at the interval 

 between the edges of the Iliacus and Psoas muscles. 



The pouch runs up under the parietal peritoneum of the posterior abdominal 

 wall and ends blind at the point of division of the inferior mesenteric artery into 

 the colica sinistra and its descending branch. More often the fossa is incom- 

 pletely subdivided by a falciform projection of the wall. Sometimes two separate 

 fossae extend from a single opening. Probably the fossa is formed by the separa- 

 tion of the two layers of the peritoneum behind the descending colon which 



