THE DUODENUM 431 



left side of the second lumbar vertebra. It is about 2 inches 

 long. This portion ends in the duodenojejunal flexure, being 

 held in position by the peritoneum, and the duodenojejunal 

 flexure is further bound down by the suspensory muscle of the 

 duodenum or the suspensory ligament of Treitz. This con- 

 sists of a few non-striated muscle fibers fused with connective 

 tissue. It arises from around the celiac axis and left crus, 

 to be inserted into the duodenojejunal flexure, and a portion 

 of the ascending portion of the duodenum. 



The Relations of the Duodenum. The first or superior portion 

 has above and in front the gall-bladder, the quadrate lobe 

 of the liver; behind is the gastroduodenal artery, the common 

 bile duct, the portal vein; below is the head of the pancreas. 

 It helps to form the lower boundary of the foramen of Winslow. 



The second or descending portion is crossed by the transverse 

 colon, which is attached to it by connective tissue; above 

 and in front is the right lobe of the liver; behind is the inner 

 part of right kidney, the renal vessels, and the inferior vena 

 cava; to the inner side is the common bile duct and the head 

 of the pancreas; outerside is the hepatic flexure of colon. 

 The transverse colon divides the duodenum in this portion, 

 into a supracolic and infracolic region. 



The third portion is crossed in front by the superior mesenteric 

 vessels and the mesentery; behind it rests on the inferior vena 

 cava, the aorta, and crura of the diaphragm. Above is the 

 head of the pancreas. 



The fourth or ascending portion has behind the aorta, the 

 left renal vessels, the left psoas muscle; to the right is superior 

 mesenteric vessels and the uncinate process of the head of the 

 pancreas; to the left and posterior are the duodenojejunal 

 folds and fossae. 



The arteries are the pyloric, the superior pancreaticoduodenal 

 from the hepatic, and gastroduodenal respectively; the inferior 

 pancreaticoduodenal, a branch of the superior mesenteric. 

 The veins correspond to the arteries. The superior pancreatico- 

 duodenal opens into the gastroduodenal, the inferior pan- 

 creaticoduodenal into the superior mesenteric vein. The nerves 

 are derived from the solar plexus. The lymphatics empty 

 into the celiac nodes of the preaortic group. 



