28o THE DIGESTIVE SYSTEM 



The Colic (Ileo-caecal) Valve guards the opening of the 

 ileum into the caecum and prevents the regurgitation of the 

 contents of the caecum into the ileum. It can be indicated 

 on the surface of the body at the intersection of the inter- 

 tubercular and the right lateral planes (Fig. 101). 



The Ascending Colon begins at the upper end of the caecum 

 and passes upwards on the posterior abdominal wall till it 

 reaches the inferior surface of the right lobe of the liver, 

 where it bends forwards and to the left, forming the right 

 (hepatic} flexure of the colon. It is about 6 inches long and 

 it lies behind the peritoneum, save in exceptional cases where 

 it possesses a dorsal mesentery. 



This part of the colon can be mapped out on the surface 

 to the lateral side of the right lateral plane, and it extends 

 from the intertubercular plane to the ninth costal cartilage 

 (Fig. 101). 



The Right Colic Flexure is placed under cover of the right 

 costal margin. Posteriorly it lies on the right kidney, and 

 anteriorly it is related to the liver and the gall-bladder. In 

 this situation the colon and the gall-bladder may become 

 adherent to one another following cholecystitis, and gall-stones 

 may find their way into the gut and be discharged per anum. 



The Transverse Colon is about 20 inches long and it forms 

 a U-shaped loop, which is suspended from the posterior 

 abdominal wall by the transverse mesocolon. 



It extends from the right flexure to the left (splenic) 

 flexure of the colon, both of which'are, within limits, fixed in 

 position. The transverse colon, however, by virtue of its 

 mesentery, may alter its position from time to time and, in 

 radiograms taken in the vertical posture, its lowest point is 

 usually a little above the upper border of the pubic 

 symphysis, but it may descend still farther without justifying 

 a diagnosis of viscero-ptosis. 



When the patient is in the dorsal decubitus, the transverse 

 colon may be indicated as a widely open U, The lower 

 border lies at, or a little below, the umbilicus, while the left 



