Paidas C N, Morreale R F, Holoski K M, Lund R E, Hutchins G M
Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, MD, USA.
J Pediatr Surg. 1999 May;34(5):877-84. doi: 10.1016/s0022-3468(99)90391-3.
BACKGROUND/PURPOSE: Limitations in methodologies have fostered controversy regarding the septation of the human embryonic cloaca. The aim of this study was to evaluate the septation of the human embryonic cloaca.
Using the Carnegie Embryological Collection and specimens at Johns Hopkins, Baltimore, MD, the authors studied 12 embryos and five fetuses. Embryo photomicrographs were reconstructed using three-dimensional modeling.
In Carnegie stage 13 the authors observed a cloaca, distinct primitive urogenital sinus, and anorectum separated by the urorectal septum. The primitive urogenital sinus and anorectum enter the cloaca separated from the amniotic space by the cloacal membrane. As the embryo becomes a fetus it lengthens, grows, expands and rotates through a process called transformation. Transformation gives rise to a loss of caudal curvature and a decrease in distance between the septum and membrane, but these structures do not fuse. Disintegration of the cloacal membrane produces openings for the urogenital sinus and anorectum.
The observations suggest that the urogenital sinus and anorectum form early and are separated by the urorectal septum as a passive structure. There does not appear to be septation or differentiation of the cloaca itself.
背景/目的：方法学上的局限性引发了关于人类胚胎泄殖腔分隔的争议。本研究的目的是评估人类胚胎泄殖腔的分隔情况。
作者利用卡内基胚胎学藏品以及位于马里兰州巴尔的摩市约翰·霍普金斯大学的标本，研究了12个胚胎和5个胎儿。通过三维建模重建胚胎显微照片。
在卡内基第13期，作者观察到一个泄殖腔、明显的原始泌尿生殖窦和由尿直肠隔分隔的肛管直肠。原始泌尿生殖窦和肛管直肠通过泄殖腔膜与羊膜腔分隔进入泄殖腔。随着胚胎发育成胎儿，它通过一个称为转化的过程变长、生长、扩张并旋转。转化导致尾曲消失以及隔与膜之间的距离减小，但这些结构并未融合。泄殖腔膜的解体为泌尿生殖窦和肛管直肠形成开口。
这些观察结果表明，泌尿生殖窦和肛管直肠形成较早，并被作为被动结构的尿直肠隔分隔。泄殖腔本身似乎不存在分隔或分化。
