Mammals can be divided into the large intestine and rectum colon, rectum directly to anal opening in vitro (cloaca disappear), mammals and amphibians, reptiles, birds of the significant differences.

• 哺乳动物的大肠可分为结肠与直肠，直肠直接以肛门开口于体外（泄殖腔消失），是哺乳类与两栖类、爬行类、鸟类的显著区别。