rectum /rek″təm/ pl. rectums, recta [L, rectus] , the lower part of the large intestine, about 12 cm long, continuous with the descending sigmoid colon, proximal to the anal canal. It follows the sacrococcygeal curve, ends in the anal canal, and usually contains three transverse semilunar folds: one situated proximally on the right side, a second one extending inward from the left side, and the third and largest fold projecting caudally. Each fold is about 12 mm wide. The folds overlap when the intestine is empty or defecation occurs. −rectal, adj.
