小肠从幽门以下开始直到回盲瓣结束 ,人类的小肠占消化道全长的 3/4左右。Treitz韧带以上的十二指肠 ,普通胃镜即能检查 ,末端回肠可以通过结肠镜检查。但Tre itz韧带以下的空肠、回肠均有肠系膜附着 ,肠管活动度较大 ,游离在腹腔内 ,被肠系膜束缚形成多发复合肠襻 ,同时空肠、 The small intestine starts from below the pylorus till the end of the ileocecal valve. The human small intestine accounts for about 3/4 of the total length of the digestive tract. The duodenum above the Treitz ligament can be examined by ordinary gastroscopy, and the terminal ileum can be colonoscopically examined. But Treitz ligament following jejunum, ileum has mesenteric attachment, greater intestinal activity, free intraperitoneal, mesenteric formation of multiple complex bowel loop, and jejunum,