270 THE ORGANS OF DIGESTION 



intestine into the large gut. This junction is oblique 

 and situated about 2 \ inches above the lower extremity 

 of the cecum. It is a double fold lying transversely 

 to the long axis of the colon. Each fold of the valve 

 is made up of the mucous and submucous coats, 

 reinforced by some circular fibers from the muscular 

 coat, of each portion of the gut, and is covered on the 

 side toward the ileum with villi. 



The Colon. The ascending colon runs from the 

 cecum, above the ileocecal valve, upward to the under 

 surface of the liver on the right side of the gall-bladder, 

 and then turns forward and to the left to form the 

 hepatic flexure. The peritoneum rarely forms for it 

 a mesocolon; generally it covers only the front part 

 and the sides. It occupies the right lumbar and 

 hypochondriac regions. 



The transverse colon arches across the abdomen, the 

 convexity looking toward the belly wall, and makes 

 a sudden turn backward and downward beneath the 

 spleen, forming the splenic flexure, and is completely 

 invested by the peritoneum, which holds it to the 

 anterior aspect of the pancreas and second portion 

 of the duodenum; by two layers of peritoneum called 

 the transverse mesocolon, the upper surface of which 

 fuses with the posterior layer of the great omentum. 

 It occupies the right hypochondriac, upper part of 

 umbilical, and left hypochondriac regions. At the 

 splenic flexure is attached the phrenocolic ligament, a 

 fold of peritoneum extending to the diaphragm 

 opposite the tenth or eleventh rib. 



The descending colon descends from the splenic 

 flexure, to end at the left iliac fossa in the sigmoid 

 flexure. It is covered in front and laterally by the 

 peritoneum. It occupies the left hypochondriac and 

 lumbar regions. 



The sigmoid flexure ends in the rectum. From the 

 end of the descending colon it forms an S-shaped 

 curve, ending opposite the left sacro-iliac joint. In 



