502 A MANUAL OF ANATOMY. 



the third portion of the duodenum. Below, the small in- 

 testine. In front it is covered by the great omentum. 

 Its mesentery is attached to the posterior abdominal wall 

 over the duodenum and pancreas, it passes to enclose the 

 colon then drops downward to form the greater omentum, 

 then rises to the lower border of the stomach, and first por- 

 tion of the duodenum. See Diag. 40. 



The splenic flexure is in contact with the spleen above. 

 From its outer margin the transverse mesocolon is con- 

 tinued to the under surface of the abdomen over the tenth 

 rib. This band is the costocolic ligament, and its func- 

 tion is to support the spleen (sustentaculum splenis). 



The descending colon (Figs. 98, 101, 102) extends from 

 the splenic flexure to the left iliac fossa. It is covered in 

 front and at the sides by peritoneum, its posterior surface 

 being usually in contact with the abdominal wall. But, as 

 with the ascending colon, this part of the colon may have 

 a distinct mesentery. In this case the peritoneal cavity 

 would be opened in performing lumbar colotomy ; if there 

 is no mesentery the gut can be cut into without invading 

 the general peritoneal cavity. 



Relations. In front and at the sides, the small intestine. 

 Behind, the diaphragm, left kidney, quadratus lumborum 

 muscle. 



The omega loop, or sigmoid flexure (Figs. 96, 97, 98, 

 101, 102), is the next part of the bowel below the descend- 

 ing colon. It lies in the left iliac fossa, reaching into the 

 pelvic cavity as low as the third portion of the sacrum, in- 

 cluding in its extent the so-called first portion of the rectum, 

 when that part of the bowel is described in three portions. 

 Its length is 18 inches. When distended the apex of the 

 loop may reach over to the right so far as to come in 

 contact with the caecum. At its lower end it is provided 



