1036 



THE ORGANS OF DIGESTION. 



FIG. 656. Extreme downward bend in the trans- 

 verse colon. Found in four cases. (Treves.) 



or left colic flexure, which is higher up and farther back than the hepatic flexure. 

 To this bend a fold of peritoneum is attached, rising from the diaphragm between 

 the tenth and eleventh ribs. It is the phreno-colic ligament, rather than " costo- 



colic," as it does not touch a rib. The 

 spleen happens to lie just above it, so it 

 acts as a support to that organ though 

 not connected with it, and thus receives 

 a second name, sustentaculum lienis (sup- 

 porter of the spleen). The colon then 

 descends along the outer border of the 

 left kidney, then turns in a little, and 

 descends to the crest of the ilium or to a 

 point where the peritoneum begins to 

 surround the intestine and form a meso- 

 colon for the sigmoid flexure. 



It has passed along the outer border 

 of the Psoas muscle in front of part of 

 the Quadratus lumborum, and more largely 

 in front of the Transversalis muscle. The 

 relations of the descending colon on the 

 left side are much like those of the as- 

 cending on the right, only the former 

 reaches a little higher and is placed more 

 laterally, so it can be more easily reached 

 through the posterior abdominal wall for the establishment of an artificial anus. 

 This colon is smaller and deeper than the ascending colon and more liable to 

 have a mesocolon. 



The sigmoid colon or flexure is in the left iliac fossa, commencing above at the 

 iliac crest and ending below in the rectum at the brim of the true pelvis opposite 

 the left sacro-iliac articulation, or just as often opposite the upper edge of the 

 sacrum. In general it is described as an S-shaped curve in which can be distin- 

 guished an upper colic limb turned toward Poupart's ligament, and a lower rectal 

 limb which hangs more or less into the true pelvis. 



This first part usually passes downward, inward, and somewhat forward, 

 approaching the anterior abdominal wall and outer part of Poupart's ligament. 

 This portion may have peritoneum only in front and on the sides. The next 

 part is more movable, its mesentery is about three inches long, and it constitutes 

 the sigmoid loop proper. When it does not hang down into the pelvis, the blad- 

 der and rectum are distended and push it up, in rare cases as high as the umbili- 

 cus or even liver. This loop may lie in the iliac fossa outside the first part ; if 

 its mesocolon is short, it passes obliquely across the iliac fossa and is covered by 

 small intestine. 



The sigmoid mesocolon is inserted into a line running from the left at the 

 crest of the ilium across the psoas muscle and left iliac vessels at right angles to 

 the anterior surface of the sacral promontory, where it is continuous Avith the 

 mesorectum (Fig. 614). In the left layer of this mesentery is the intersigmoid 

 fossa (page 996). The position of the flexure in the new-born demands notice, 

 for here the mesentery is very long and the flexure may reach over on the right 

 to the caecum. This flexure is usually filled with meconium. 



Relations of Large Intestine in Detail. 



Caecum. 

 Anteriorly : 



Anterior abdominal wall above outer half of Poupart's ligament. 

 Posteriorly : 



Right ilio-psoas muscle ; Origin of appendix. 



