1162 



DIGESTIVE SYSTEM 



Position and relations. — As shown in fig. 914, the duodenum usually lies 

 chiefly in the lower part of the epigastric region, only the inferior (transverse) 

 portion extending into the umbiUcal region. All but the terminal (ascending) 

 portion of the duodenum Ues to the right of the mid-line. 



The superior portion usually lies at the level of the first lumbar vertebra (or 

 the disk below). It is covered anteriorly, and to a variable extent posteriorly, 

 by a prolongation of the peritoneum from the corresponding surfaces of the 

 stomach. It is somewhat freely movable. When the stomach is empty, it 

 extends from the pylorus almost horizontally to the right and backward. As 

 the stomach becomes distended, however, the pylorus is carried to the right and 

 downward for a variable distance, and the position of the superior part of the 

 duodenum is correspondingly altered. 



Superiorly it is in contact with the Hver (quadrate lobe) and the neck of the gall-bladder 

 and forms the lower boundary of the epiploic foramen; anteriorly, with the liver and (often) 

 the transverse colon; inferiorly and posteriorly, with the head of the pancreas below, and with 

 the common bile duct, hepatic vessels and portal vein above. 



The second or descending portion of the duodenum extends along the right 

 side of the first to the third lumbar vertebra. It is covered antero-laterally by 

 peritoneum, excepting (usually) the area of contact with the transverse colon 

 (figs. 906, 920). 



Posteriorly (fig. 956) it is in contact with the right kidney, ureter and renal vessels, and below 

 with the psoas muscle. Anteriorly (fig. 906) it is crossed by the transverse colon (the layers of 

 the transverse mesocolon usually separated by an area of direct contact); above the colon, it 

 may be in contact with the gall-bladder, and below the colon with coils of small intestine. The 



Fig. 921. — The Duodenum and Pancreas, Posterior View. 



Portal vein 



- Common bile- 

 duct 



Terminal part of duodenum 



Head of pancreas 



left or medial aspect of the descending duodenum (figs. 920, 921, 922) is in contact with the 

 head of the pancreas, and some fibres from the muscular tunic are said to become intermingled 

 with the pancreatic lobules. Somewhat posteriorly the common bile duct descends between 

 pancreas and duodenum, and enters the descending duodenum, in common with the pancreatic 

 duct, about 10 cm. below the pylorus. The loop formed by the pancreatico-duodenal arteries 

 also runs along the descending duodenum. 



The third or transverse portion of the duodenum usually crosses the body of 

 the third lumbar vertebra, ascending slightly from the right to the left side 

 (figs. 920, 921). It is covered anteriorly with peritoneum, excepting a small 

 space where the superior mesenteric vessels enter the root of the mesentery. 



Anteriorly it is further in contact with coils of small intestine; superiorly, with the head of 

 the pancreas, and the inferior pancreatico-duodenal vessels; posteriorly, with the vena cava. 



The terminal or ascending portion is covered anteriorly and laterally by 

 peritoneum, and is in contact with coils of the ileum. To the right it is in rela- 

 tion with the head of the pancreas (i)rocessus uncinatus) and the superior mesen- 

 teric ves.sels; and posteriorly with the psoas muscle, aorta and left renal vessels. 

 The duodeno-jcjnnal flexure usually lies op])osite the second lumbar vertebra, and 

 is in contact above with the inferior surface of the body of the pancreas, and the 

 root of the transverse mesocolon. 



