1174 DIGESTIVE SYSTEM 



peritoneum, extending from the right side of the gut to the abdominal wall at a 

 little above the level of the highest part of the iliac crest. It forms a shelf upon 

 which rests the extreme right margin of the liver. It might be called the susten- 

 taculuyn hepatis. 



The ascending colon is in relation behind with the right kidney, and the iliacus 

 and quadratus lumborum. In front are some of the coils of the ileum (fig. 899), 

 separating it from the anterior abdominal wall. 



The transverse colon. — The transverse colon [colon transversum], smaller in 

 diameter than the ascending, extends from the lower surface of the liver to the 

 spleen. Its average length is from 40 to 50 cm. It describes an arch with its 

 convexity forward and downward. It crosses through the umbilical region from 

 the right hypochondrium to the left hypochondrium (figs. 899, 906, 914). 



In the majority of cases the superficial part of the colic arch — as seen before 

 the viscera are disturbed — is either in whole or in greater part above a straight 

 line drawn transversely across the body between the highest points of the iliac 

 crest. In about one-fourth of all cases it lies, in whole or in greater part, below 

 this line. 



Certain remarkable bends are sometimes formed by this part of the bowel. 

 The bending is always in the same direction, namely, downward, and is usually 

 abrupt and angular. The apex of the V or U-shaped bend thus formed may reach 

 the pubes. This bend appears to be due to two distinct causes: namely, long- 

 continued distention, on the one hand, and congenital malformation on the other. 



The transverse colon is in relation above with the liver and gall-bladder, the 

 stomach, and at its left extremity with the spleen. The second portion of the 

 duodenum passes behind it. Below are the coils of the small intestine. It is 

 almost completely surrounded by peritoneum, being connected with the posterior 

 abdominal wall (chiefly the anterior border of the pancreas) by the transverse mes- 

 ocolon. This is usually lacking on the right of the mid-line, however, where the 

 colon crosses the descending duodenum and the head of the pancreas (fig. 905). 



The descending colon [colon descendens] is 25 cm. to 30 cm. in length (less 

 when in situ) and extends from the spleen to the pelvic brim (figs. 906, 914). It 

 is more movable than the ascending colon and is also narrower. At its beginning 

 it is usually connected with the diaphragm, on a level with the tenth and eleventh 

 ribs, by a fold of peritoneum, the phreno-colic ligament [lig. phrenicocolicum] 

 (or sustentaculum lienis, from the fact that it supports the spleen). The bend 

 between the transverse colon and descending colon is called the left colic or splenic 

 flexure [flexura coli sinistra]. The descending colon is situated in the left hypo- 

 chondriac, lumbar and iliac regions (fig. 906). Its relations to the peritoneum 

 are the same as obtain with the ascending colon, that is, it is covered in front and 

 on the sides. A mesocolon is met with oftener on this side than on the light, 

 occurring in 36 per cent, of all cases (Treves) (see fig. 902). It is found especially 

 in the lower part of the descending colon, in the iliac fossa. This portion, extend- 

 ing from the iliac crest to the brim (superior aperture) of the pelvis, is sometimes 

 described as a separate segment, the iliac colon (Jonnesco). 



The descending colon is covered anteriorly by coils of small intestine; pos- 

 teriorly it is in contact with the lower part of the left kidney, the quadiatus lum- 

 borum, iliacus and psoas muscles. It terminates by crossing medialward over the 

 psoas muscle and the external iliac vessels to join the sigmoid colon. 



The sigmoid colon [colon sigmoideum] or pelvic colon, extends from the 

 descending colon to the rectum (figs. 906, 914). It includes what was formerly 

 described as the 'sigmoid flexure' and also the 'first portion' of the rectum. 

 These together form a single loop which cannot conveniently be divided into parts. 



The loop, the sigmoid colon, begins at the margin of the psoas, and ends where 

 the sigmoid mesocolon ceases, opposite the second or third sacral vertebra. 



The loop when unfolded describes a figure that may be compared to the capital 

 omega. Ilie average; length of this sigmoid colon is about 40 cm. The normal 

 position of the loop is not in the left ihac fossa, })ut wholly in the pelvis. The most 

 conimon (hsposition of it may now be described. 'J'he sigmoid (pelvic) colon 

 begins about midway between the lumbo-sacral eminence and the inguinal 

 (Poupart's) ligament. It descends at first along the left pelvic wall, and may at 

 once reach the pelvic floor. It then passes more or less horizontally and trans- 

 versely across the pelvis from left to right, and commonly comes into contact with 

 the right pelvic wall. At this point it is bent upon itself, and, passing once more 



