498 A MANUAL OF ANA TO MY. 



Relations. Above and in front, liver, gall bladder, fora- 

 men of Winslow. Below, pancreas. Behind, the common 

 bile and pancreatic duct, and vessels passing to the liver. 



(2) The descending 1 portion is two and three-fourths 

 inches long, and extends from the neck of the gall bladder 

 to the level of the second or third lumbar vertebra. 



Relations. Front, transverse colon and mesocolon. To 

 the left, pancreas. To the left and posterior, the common bile 

 duct. Behind, the right kidney, renal vessels, and vena cava. 



This portion of the duodenum is covered only in front by 

 the peritoneum. Into this part of the duodenum the com- 

 mon bile and pancreatic duct opens, at a point four inches 

 from the pylorus. 



(3) The third or transverse portion of the duodenum, 

 four or five inches long, is the most fixed portion of the 

 alimentary canal. It crosses the spine over the second or 

 third lumbar vertebra, in a slightly oblique direction, the 

 right end being a little lower than the left. 



Relations. In front, it is covered by the peritoneum, 

 transverse colon and mesocolon, and the superior mesen- 

 teric artery. Above, the pancreas, inferior pancreaticoduo- 

 denalis artery, the superior mesenteric artery and vein. 

 Behind, the crura of the diaphragm, vena cava, aorta. 



(4) The fourth or distal ascending portion, usually 

 described as a part of the third portion. This part is only 

 one inch long, curves vertically upward, is nearly covered 

 by peritoneum. It is held in position by a process of peri- 

 toneum containing some muscular fibres and called the 

 musculus suspensorius duodeni (of Treitz), which extends 

 from the left crus of the diaphragm and tissues about the 

 cceliac axis. Behind this band is the small fossa duo- 

 denojejunalis, opening upward, and into which a retro- 

 peritoneal hernia might possibly find its way. 



