The rectum is a part of the lower gastrointestinal tract. It is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. The adult human rectum is about 12 centimetres (4.7 in) long. In humans, the rectum is followed by the anal canal which is about 4 centimetres (1.6 in) long, before the gastrointestinal tract terminates at the anal verge. The word rectum comes from the Latin rectum intestinum, meaning straight intestine.
The rectum acts as a temporary storage site for feces. The rectum receives fecal material from the descending colon, transmitted through regular muscle contractions called peristalsis. As the rectal walls expand due to the materials filling it from within, stretch receptors from the nervous system located in the rectal walls stimulate the desire to pass feces, a process called defecation.
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