498 ABDOMEN 



venience of description the duodenum is divided into four 

 parts (i) superior, (2) descending, (3) inferior, (4) ascending. 

 The greater portion of the first part is surrounded by 

 peritoneum which is continuous below with the great omentum 

 and above with the gastro-hepatic omentum, but its terminal 

 portion is devoid of peritoneum posteriorly and inferiorly. The 

 second part is covered by the peritoneum in front, and on the 

 right side, except where it is crossed by the transverse colon, 

 the third part is covered in front and below, and the fourth 

 part is covered in front and on the left side. The remaining 

 surfaces of the second, third, and fourth parts of the 

 duodenum are devoid of peritoneum, and they lie in relation 

 either with other viscera, with large blood-vessels, or with 

 the posterior wall of the abdomen. 



Pars Superior. The first part of the duodenum is two 

 inches in length, it lies in the epigastric region, and for about 

 an inch or more from the pylorus it is enveloped by the 

 same two layers of peritoneum which invest the stomach, 

 consequently it enjoys a limited degree of movement ; in its 

 terminal part it is only covered on its anterior and superior 

 surfaces by the peritoneum. Its position and relations are 

 dependent upon the degree of distension of the stomach. 

 When that viscus is empty and the pylorus, in consequence, 

 lies close to the medial plane, the first part of the duodenum 

 passes backwards and to the right, with a slightly upward 

 inclination, in correspondence with the slope of the visceral 

 surface of the liver, until it reaches the neck of the gall-bladder. 

 Here it ends by bending suddenly downwards into the second 

 part. Under these circumstances the superior part of the 

 duodenum lies in close apposition with the lobus quadratus of 

 the liver. When the stomach, on the other hand, is dis- 

 tended the pylorus comes into relation with the lobus 

 quadratus, and the superior part of the duodenum is some- 

 what shortened and proceeds straight backwards. It then 

 occupies only the posterior part of its original situation, and 

 its termination is lodged in a depression at the right end of 

 the porta hepatis. The relations of the first part of the 

 duodenum are as follows : above and in front, the under 

 surface of the liver ; below, the pancreas ; behind, the common 

 bile-duct, the gastro-duodenal artery, the upper part of the 

 neck of the pancreas, and the portal vein. 



Pars Descendens. The second part of the duodenum is 



