THE DUODENUM. 



1647 



fold the upper surface of the first part of the duodenum is covered by peritoneum 

 and forms the floor of the foramen of Winslow. The attachment of the greater 

 omentum, which is continued from the greater curvature of the stomach onto the 

 under side of the duodenum, passes along its inferior surface to the second part, 

 where in the adult it has fused with the mesentery of the transverse colon. The peri- 

 toneum of the right side of the first part of the duodenum looks into the general 

 peritoneal cavity and that of the left side into the lesser cavity. 



The relations of the remainder of the duodeuum necessarily vary with the dis- 

 tention of the intestine ; but it is correct to say that it lies behind the peritoneum, 

 owing to the change into connective tissue subsequent to the fusion of the serous 

 membrane of the right side of the duodenum and that of the posterior abdominal 

 wall. Very often when the fourth part lies in front of the aorta a fold of peritoneum 

 passes some distance in between them from the left ; but this pocket disappears when 

 the gut is distended. The pancreas, when it overlaps the second, third, or even the 

 fourth part, more or less displaces the peritoneum. The duodenum is crossed by 

 the attachment of the mesentery of the jejuno-ileum and by that of the transverse 

 mesocolon. The series of changes by which this has occurred is dealt with under 



Fig. 1400. 



Jejunum 



Transverse mesocolon 



Duodenum 



Superior 

 ^ , , duodenal fossa 



.ii_4_i|_Branch of left 

 Wm colic artery 



Inferior duodenal 

 fossa 



-^f — Descending colon 



M 



iM Mesentery of small 



"" intestine 



Duodeno-jejunal junction, showing duodenal fossae ; jejunum turned to the right. 



Peritoneum (page 1742), the adult condition alone being here considered. The line 

 of attachment of the transverse mesocolon crosses the second part of the duodenum 

 a little below the deep flexure which on the front separates it from the first. The 

 position of the line of attachment of the mesentery of the jejuno-ileum varies with 

 the shape and position of the duodenum. Should the latter have its third part 

 crossing the aorta, the attachment of the mesentery will cross the third part only, 

 passing somewhat obliquely downward to the right. In the more usual arrangement, 

 in which the fourth part of the duodenum either ends on the front of the aorta or 

 crosses it only just before its termination, the line of attachment starts on the front 

 of the fourth part or somewhat on the right of it and descends on more or less, 

 sometimes on the whole length of this portion, or else lies just to the right of it and 

 then crosses the third part. In the case of the V-shaped duodenum the mesentery 

 runs down on or along the right of the oblique portion. 



Duodeno-jejunal Fossae. — Several pockets formed by folds of peritoneum 

 are found near the end of the duodenum in the greater cavity of the peritoneum. 

 Some are vascular, — that is, containing a vessel at or near the edge of the fold, — while 

 others are not. We have adopted the classification of Jonnesco, who describes five 

 forms. 



