ABDOMINAL CAVJJfY 



gastro-duodenal artery, the portal veii^nu the upper part of 

 the neck of the pancreas. 



Pars Descendens. The descending part of the duodenum is 

 from 7.5 to 10 cm. (three to four inches) in length. At its 

 commencement it lies in the epigastric region, immediately 

 below the liver, and it descends, along the medial face of the 

 right lateral plane, into the umbilical region, to the level of 

 the middle of the third lumbar vertebra, where it turns to 

 the left and joins the inferior part. It is immovably fixed in 

 its position ; it is covered with peritoneum only on its anterior 

 and right lateral surfaces, and it is crossed by the commence- 

 ment of the transverse colon which does not possess a mesentery, 

 and is therefore in direct contact with the descending part of 

 the duodenum (Fig. 156). Posteriorly, it rests upon the right 

 border of the inferior vena cava and presents a variable 

 relation to the renal vessels and the anterior surface of the 

 right kidney in the neighbourhood of the hilum. To the 

 right is the right flexure of the colon ; and its left side is in 

 contact with the head of the pancreas, which is moulded upon 

 the medial side of the descending part of the duodenum. 



The bile-duct and the pancreatic duct open into the 

 descending part of the duodenum a little below its middle, 

 at the junction of its medial and posterior aspects. 



Pars Inferior. The first or horizontal portion of the 

 inferior part of the duodenum crosses the posterior wall of 

 the abdomen at the level of the third lumbar vertebra, its 

 direction being from right to left and slightly upwards. To 

 the right of the median plane it lies in the upper part of 

 the umbilical region, but near its termination it rises above 

 the subcostal plane into the epigastric region. Its anterior 

 and inferior surfaces are covered with peritoneum. It lies 

 behind the transverse colon ; and it is crossed by the upper 

 part of the root of the mesentery of the small intestine, con- 

 taining the superior mesenteric artery and vein. Posteriorly, 

 it rests against the right ureter, the right psoas major muscle, 

 the right internal spermatic artery, the inferior vena cava, and 

 the abdominal part of the aorta (Fig. 156). Its upper border 

 is in relation with the head of the pancreas and the inferior 

 pancreatico-duodenal artery; and its lower border is in 

 relation with coils of the jejunum. 



The second or ascending portion of the inferior part of 

 the duodenum passes upwards from the level of the upper 



