282 THE DIGESTIVE SYSTEM 



As it descends through the pelvis, the rectum follows the 

 curve of the sacrum and coccyx, and i inch in front of the tip 

 of the coccyx it bends sharply backwards and downwards to 

 join the anal canal. When it is examined in situ from in 

 front it is found that the rectum bulges to the left side of the 

 median plane. It possesses three lateral flexures. At first it 

 bends to the left and then to the right, so as to regain the 



FIG. 102. The Rectal Valves. 



An oblique frontal (coronal) section has been made through the pelvis so as to pass 

 through the anal canal. In addition, the anterior wall of the rectum has been 

 removed and the rectal valves (x) are exposed. The lateral flexures of the 

 rectum are well shown. 



median plane, but it does not pass over to the right side. 

 Instead, it bends for a third time, so that its lower part lies in 

 the middle line. On the concave side of the lateral flexures, 

 the mucous membrane projects into the lumen of the gut 

 forming horizontal folds, termed the rectal valves. The 

 highest and the lowest of the three lie on the left wall of the 

 gut, while the middle valve lies on the right wall. The lowest 

 valve can be reached with the tip of the finger on rectal 



