338 SURGICAL APPLIED ANATOMY. [Chap. xvn. 



The duodenum and fossa diiodeno- 

 jejnnalis. The first portion of the duodenum is 

 nearly horizontal. It measures about two inches in 

 length and passes backwards from the pylorus to near 

 the upper end of the right kidney. The second 

 portion, about three inches in length, descends verti- 

 cally in front of the inner border of the right kidney 

 to the level of the third lumbar vertebra. The third 

 portion, some five inches in length, crosses from 

 right to left in front of the third vertebra, and then 

 ascends for a short distance on the surface of the left 

 psoas muscle, to end in the jejunum to the left of the 

 second lumbar vertebra. The first portion, which is 

 movable, is invested by peritoneum, in the same 

 manner as the stomach. The second part is covered 

 by peritoneum in front only, except at the spot where 

 it is crossed by the transverse colon. The third pai't 

 is also covered by peritoneum only on its anterior 

 aspect, this membrane being, however, free of the 

 gut where the superior mesenteric vessels cross it. 



The first portion has found its way into hernise in 

 company with the stomach, but the second and third 

 parts are never herniated. The end of the duodenum, 

 the duodeno-jejunal bend, is very firmly held in place 

 by a band of fibrous tissue that descends upon it from 

 the left crus of the diaphragm and the tissue about 

 the cceliac axis. This band is called the suspensory 

 muscle of the duodenum (Treitz). It serves also to 

 support the mesentery. No matter to what extent 

 the stomach may be displaced by distension, or the 

 intestines disturbed by a like cause, the position of the 

 duodeno-jejunal bend will be found to remain un- 

 altered. All sections of the duodenum have been- 

 ruptured by violence. Owing to its large non-peri- 

 toneal surface, the bowel, if approached from behind, 

 may be wounded without opening the peritoneum 

 (Fig. 33). 



