Rectum and anal canal (English)

The rectum extends from the rectosigmoid junction superiorly to the anorectal junction inferiorly. Four transverse folds create the three lateral flexures of the rectum (superior, intermediate, and inferior). The anal canal houses the anal columns, which are connected to each other distally end by folds known as anal valves. Found between the anal columns are anal sinuses, into which the excretory ducts of the anal glands open. The anal valves form an irregular line called the pectinate line, which is an important anatomic landmark. The anal canal extends down to the anocutaneous line, which represents its transition into the anus and perianal skin. The region between the pectinate line and anocutaneous line is termed as the anal pecten. The internal anal sphincter can be seen surrounding the upper two thirds of the anal canal, whereas the external anal sphincter is observed external to the lower two thirds of the anal canal. The levator ani muscle can be seen extending inferiorly, where its puboanalis part (puboanalis, a.k.a. puborectalis muscle) slings around the anorectal junction. The region constituted by adipose tissue that is interposed in between the anal canal and the ischium is termed ischioanal fossa.