THE DUODENUM 253 



THE SMALL INTESTINE 



The Duodenum begins at the pylorus on the right side of 

 the body of the first lumbar vertebra and terminates at the 

 duodeno-jejunal flexure on the left side of the second lumbar 

 vertebra. Between these two points, it forms a C-shaped bend, 

 which encloses the head of the pancreas. 



The first part of the duodenum passes backwards, upwards 

 and to the right in relation to the gall-bladder and the inferior 

 surface of the liver. It lies in front of the bile-duct, portal 

 vein, inferior vena cava and gastro-duodenal artery, and, 

 although its terminal portion is covered by peritoneum only 

 anteriorly, its commencement is covered both anteriorly and 

 posteriorly. This latter fact accounts for the descent of the 

 pylorus when the erect attitude is adopted. In radiograms, 

 after the bismuth meal has passed through the pyloric canal, 

 the commencement of the duodenum throws a shadow, which 

 lies immediately above the pylorus (Fig. 94). 



Duodenal ulcers are usually situated on the antero-lateral 

 wall of the first part of the duodenum. A small area in this 

 situation is very constantly supplied by a special branch from 

 the hepatic artery, and it has been suggested that this vessel is 

 an end-artery and that the area in question is therefore not so 

 richly supplied with blood as the rest of the duodenum. An 

 ulcer in the posterior wall of this part of the duodenum may 

 cause death from haemorrhage by eroding the gastro-duodenal 

 artery (Fig. 91). 



The second part of the duodenum runs downwards in front 

 of the hilum of the right kidney and extends to the lower 

 border of the third lumbar vertebra. A little below its middle 

 it is crossed by the transverse colon, and so its upper part lies 

 in the supra-colic compartment, while its lower part is on the 

 posterior wall of the right infra-colic compartment. The 

 second part of the duodenum receives the secretions of the 

 liver and the pancreas (pp. 262 and 269). 



The third part of the duodenum passes to the left and, after 



