1286 



THE ORGANS OF DIGESTION 



to left, with a slight inclination upward, in front of the great vessels and crura 

 of the Diaphragm, and ends in the fourth portion in front of or just to the left 

 of the abdominal aorta. It is crossed by the superior mesenteric vessels and the 

 mesentery. Its ventral surface is covered by peritoneum, except near the middle 

 line, where it is crossed by the superior mesenteric vessels (Fig. 1010). Its posterior 

 surface rests upon the aorta, the inferior vena cava, and the crura of the Diaphragm. 

 Its upper surface is in relation with the head of the pancreas. The left side of 

 the termination of the ascending portion is also covered by peritoneum, and in 

 this region some of the duodenal fossae are found (p. 1266). 



The fourth or ascending portion of the duodenum (pars ascendens} (Figs. 

 1007 and 1011) is about an inch (2.5 cm.) long. It ascends on the left side of 

 the vertebral column and aorta, as far as the level of the upper border of the second 

 lumbar vertebra, where it turns abruptly forward to become the jejunum, forming 

 the duodenojejunal flexure (flexura duodenojejunalis) (Fig. 1012). It lies in front 

 of the left Psoas muscle and left renal vessels, and is covered in front, and partly 

 at the sides, by peritoneum, continuous with the left portion of the mesentery 

 (Fig. 1011). 



LOBE OF 

 SPIGELIUS 



CELLULAR MEMBRANE 



CONNECTING THE PARTS 



OFTHE DUODENAL RING 



BEHIND THE PANCREAS 



DIAPHRAGM 



CCELIAC AXIS 



GANGLION OF 

 CCELIAC PLEXUS 

 SUPERIOR MESEN- 

 TERIC ARTERY 



SUSPENSORY 

 MUSCLE OF 

 DUODENUM 



FIG. 1012. Suspensory muscle of the duodenum or muscle of Treitz. (Poirier and Charpy.) 



The first part of the duodenum, as stated above, is somewhat movable, but 

 the rest is practically fixed and is bound down to neighboring viscera and the 

 posterior abdominal wall by the peritoneum. In addition to this, the fourth part 

 of the duodenum and the duodenojejunal flexure is further bound down and fixed 

 by a structure called the Suspensory muscle of the duodenum or the suspensory 

 ligament of Treitz (m. suspensorim duodeni) (Fig. 1012). This structure commences 

 in the connective tissue around the cceliac axis and left crus of the Diaphragm, 

 and passes downward to be inserted into the superior Border of the duodenojejunal 

 curve and a part of the ascending duodenum, and from this it is continued into the 

 mesentery. It possesses, according to Treitz, some few nonstriated muscle fibres 

 mixed with the fibrous tissue, of which it is principally made up. It is of little 

 importance as a muscle, but acts as a suspensory ligament. 



