LM of rectum, anal canal.The rectum is the final straight portion of the large intestine in humans and other mammals, and the gut in others. In humans, the rectum is followed by the anal canal, before the gastrointestinal tract terminates at the anal verge. The anal canal is the terminal part of the large intestine It is situated between the rectum and anus, below the level of the pelvic diaphragm. It lies in the anal triangle of perineum in between the right and left ischioanal fossa. Magnification x75.