THE SMALL INTESTIXE 



1169 



now takes a second bend, and passes from right to left across the vertebral column, 

 having a slight inclination upward; and on the left side of the vertebral column 

 it ascends for about* 2. 5 cm., and then ends opposite the second lumbar vertebra 

 in the jejunum. As it unites with the jejunum it turns abruptly forward, forming 

 the duodendojejunal flexure. From the above description it will be seen that the 

 duodenum may be divided into four portions: superior, descending, horizontal, 

 and ascending. 



Relations. The superior portion (pars superior; first portion) is about 5 cm. long. 

 Beginning at the pylorus, it ends at the neck of the gall-bladder. It is the most 

 movable of the four portions. It is almost completely covered by peritoneum, but a 

 small part of its posterior surface near the neck of the gall-bladder and the inferior 



Probe in pancreatic duct 



Probe in common "bile-duct 

 FIG. 1057. Interior of the descending portion of the duodenum, showing bile papilla. 



rena cava is uncovered; the upper border of its first half has the hepatoduodenal 

 ligament attached to it, while to the lower border of the same segment the greater 

 omentum is connected. It is in such close relation with the gall-bladder that it 

 is usually found to be stained by bile after death, especially on its anterior surface. 

 It is in relation above and in front with the quadrate lobe of the liver and the gall- 

 bladder; behind with the gastroduodenal artery, the common bile duct, and the 

 portal vein; and below and behind with the head and neck of the pancreas. 



The descending portion (pars descendens; second portion) is from 7 to 10 cm. long, and 

 extends from the neck of the gall-bladder, on a level with the first lumbar vertebra, 

 along the right side of the vertebral column as low as the upper border of the body 

 of the fourth lumbar vertebra. It is crossed in its middle third by the transverse 

 colon, the posterior surface of which is uncovered by peritoneum and is connected 

 to the duodenum by a small quantity of connective tissue. The supra- and infra- 

 colic portions are covered in front by peritoneum, the infracolic part by the right 

 leaf of the mesentery. Posteriorly the descending portion of the duodenum is not 

 covered by peritoneum. The descending portion is in relation, in front, from above 

 downward, with the duodenal impression on the right lobe of the liver, the trans- 

 verse colon, and the small intestine; behind, it has a variable relation to the front 

 of the right kidney in the neighborhood of the hilum, and is connected to it by 

 loose areolar tissue; the renal vessels, the inferior vena cava, and the Psoas below, 

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