A clinical anatomical study of the arrangement of the intrapelvic fasciae and the distribution of the nerves with special reference to the relationships to the development of the urorectal space and the pelvic plexus

在大体解剖学研究中，我们研究了盆腔内筋膜的空间排列和盆丛分支的分布。盆丛至尿路括约肌的分支一般起源于S4，为盆腔内脏神经的最低支，沿肛提肌的直肠附着处发出。阴部神经与提肛肌内侧支之间有时可见各种联系。提示从神经到肛提肌的躯体神经纤维或从阴部神经到盆丛的神经支也可能与该区域的神经支相连。此外，我们还研究了髂内动脉的分支模式。在胚胎学研究中，为了了解正常泄殖腔发育过程，从胚胎11.5天(E11.5天)到E13.5天，每隔6小时制作一次小鼠胚胎的矢状面切片。在泄殖腔发育形成泌尿生殖窦和肛门直肠管的过程中，未观察到尿肠隔与泄殖腔膜融合，泄殖腔的腹侧和背侧由泄殖腔膜连续连接，直到泄殖腔膜消失，在E13.5向外开放由泌尿生殖窦和肛门直肠管形成的前庭。此外，我们还研究了泄殖腔内凋亡细胞/小体的时空分布。结果提示，早期(至E12.0)泄殖腔背侧间充质细胞中的细胞凋亡分布可能与该部位的转化和腹移密切相关。反之，晚期(E12.0)尿直肠隔间充质细胞的凋亡模式可能参与了尿直肠隔的转化和泄殖腔膜的解体。

In a gross anatomical study, we investigated the spatial arrangement of the intrapelvic fasciae and the distribution of the branches of the pelvic plexus. The branches from the pelvic plexus to the urethral sphincter region generally originated from S4 as a lowest branch of the pelvic splanchnic nerve, and ran along the rectal attachment of the levator ani. Various connections were sometimes observed between the pudendal nerve and the branches medial to the levator ani. It is suggested that the somatic nerve fibers from the nerve to the levator ani or from the pudendal nerve might also join the nerve branches to the region from the pelvic plexus. In addition, we also investigated the branching patterns of the internal iliac artery.In a embryological study, to understand normal cloacal developmental processes, serial sagittal sections of mouse embryos were made every 6 h from embryonic day 11.5 (E11.5) to E13.5. During cloacal development to form the urogenital sinus and anorectal canal, fusion of the urorectal septum with the cloacal membrane was not observed, and the ventral and dorsal parts of the cloaca were continuously connected by the canal until disappearance of the cloacal membrane to open the vestibule formed by the urogenital sinus and anorectal canal to the outside at E13.5. In addtion, we investigated the spatiotemporal distribution of the apoptotic cells/bodies in the cloacal region. The present findings suggest that in the early stages (until E12.0), distribution of apoptosis in mesenchyme around the dorsal part of the cloaca might be strongly related to the transformation and ventral shifting of this part. Conversely, the apoptosis pattern in urorectal septum mesenchyme in later stages (from E12.0) might be involved in transformation of the urorectal septum and disintegration of the cloacal membrane.