Kim Won Kyu, Kim Hyun, Ahn Dae Ho, Kim Myoung Hee, Park Hyoung Woo
Department of Anatomy, College of Medicine, Hanyang University, Seoul, South Korea.
Birth Defects Res A Clin Mol Teratol. 2003 Nov;67(11):941-5. doi: 10.1002/bdra.10094.
The existing data on intestinal rotation during human development are contradictory regarding the timing of major events, and as such an exact timetable for rotation of the intestine in humans is not yet available.
We studied the initial formation and rotation of the intestine by microdissection and histological observations in 72 human embryos and fetuses at two to 12 weeks postfertilization. The embryos were classified according to the Carnegie staging system.
The primordium of the primitive gut was first observed as a yolk sac at stage 5. With the formation of the embryonic foldings, three divisions of the primitive gut (the foregut, midgut, and hindgut) were observed at stage 10. At stage 12, the primitive gut was located on the midline. At stage 15, a 90 degrees counterclockwise rotation of the intestine began. At stage 16, herniation of the intestine into the umbilical cord was not evident in observations of the external form or a transversely sectioned embryo, but was evident in a sagittally sectioned embryo. There was another 90 degrees counterclockwise rotation at stage 20. Reduction of the intestine was a rapid process, since it was still in the cord in fetuses of <40 mm crown-rump length (CRL), and was reduced above 40 mm in general during nine weeks of development. When the intestine returned to the abdominal cavity, the cecum was located in the right lower quadrant (the adult position).
We have developed a standard timetable to describe the rotation of the intestine. The current results will be helpful in studies describing the pathogenesis of some developmental abnormalities in the intestine due to abnormal rotation.
关于人类发育过程中肠道旋转的现有数据在主要事件发生时间上相互矛盾，因此人类肠道旋转的确切时间表尚未确定。
我们通过显微解剖和组织学观察，研究了72例受精后2至12周的人类胚胎和胎儿肠道的初始形成和旋转情况。胚胎根据卡内基分期系统进行分类。
原始肠管原基最初在第5阶段被观察为卵黄囊。随着胚胎折叠的形成，在第10阶段观察到原始肠管分为三个部分（前肠、中肠和后肠）。在第12阶段，原始肠管位于中线。在第15阶段，肠道开始逆时针旋转90度。在第16阶段，从外部形态或横向切片胚胎观察，肠道疝入脐带不明显，但在矢状切片胚胎中明显。在第20阶段又有90度逆时针旋转。肠道回纳是一个快速过程，因为在头臀长（CRL）<40mm的胎儿中肠道仍在脐带内，而在发育的9周内一般在CRL高于40mm时回纳。当肠道回到腹腔时，盲肠位于右下腹（成人位置）。
我们制定了一个描述肠道旋转的标准时间表。目前的结果将有助于研究因旋转异常导致的一些肠道发育异常的发病机制。
