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End segment of the large intestine (seedigestion) in which feces accumulate just prior to discharge. It is 5–6 in. (13–15 cm) long and lined with mucous membrane. One set of muscles separates it from the anal canal; another shortens it to expel feces. The rectal walls distend as feces enter, which stimulates the urge for defecation.
This entry comes from Encyclopædia Britannica Concise. For the full entry on rectum, visit Britannica.com.