3/9/2023 0 Comments Anorectal flextureThe rectal wall consists of five layers, starting from the lumen: the mucosa, deep mucosa, submucosa, muscularis propria, and serosa that is covered by the peritoneum. In women, the reflection is from the rectum to the posterior cervix forming the rectouterine pouch, also known as the pouch of Douglas. In men, the reflection of the peritoneum to the posterior bladder forms the rectovesical pouch. The peritoneal reflection is variable between individuals but is generally six to eight cm from the anal verge. The rectum is attached posteriorly to the presacral fascia at the level of S4 via the Waldeyer fascia. This fascia is more pronounced laterally, forming the lateral rectal stalks. The lower third is not covered by the peritoneum but starting at this level, the fascia propria envelops this segment of the rectum. The peritoneum covers the upper third of the rectum anteriorly and laterally, but the middle third is only covered anteriorly. The rectum transitions to the anal canal at the level of the levator ani muscle. ![]() The final portion of the rectum is the ampulla, which is an expanded segment that rests on the pelvic diaphragm. There are also three lateral flexures, made by submucosal folds in the lumen called valves of Houston, often two on the left and one on the right. ![]() Its course is marked by two anterior-posterior flexures, with the rectum first following the concavity of the sacrum at the sacral flexure and later coursing with an anterior convexity at the anorectal flexure. The rectum measures between 12 to 15 cm in length from the rectosigmoid junction to the dentate line in the anal canal. This portion of the GI tract is differentiated from the colon by the coalescence of taenia coli where the muscular bands spread to form the outer longitudinal muscle layer of the rectum. The rectum starts at the level of S3 around the sacral promontory as a continuation of the sigmoid colon.
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