Rectum and anal canal (Latin)

The rectum extends from the junctio rectosigmoidea superiorly to the junctio anorectalis inferiorly. Four plicae transversi create the flexurae laterales recti (superior, intermedia, and inferior). The canalis analis houses the columnae anales, which are connected to each other distally by folds known as valvulae anales. Found between the columnae anales are sinus anales, into which the excretory ducts of the anal glands open. The valvulae anales form an irregular line called the linea pectinata, which is an important anatomic landmark. The canalis analis extends down to the linea anocutanea, which represents its transition into the anus and perianal skin. The region between the linea pectinata and linea anocutanea is termed as the pecten analis. The m. sphincter internus ani can be seen surrounding the upper two thirds of the canalis analis, whereas the m. sphincter externus ani is observed external to the lower two thirds of the canalis analis. The m. levator ani can be seen extending inferiorly, where its puboanalis part (m. puboanalis, a.k.a. m. puborectalis) slings around the junctio anorectalis. The region constituted by adipose tissue that is interposed in between the anal canal and the ischium is termed fossa ischioanalis.