2006 Fiscal Year Final Research Report Summary
Comparative development study of the cloacal separation and formation of anal canal
| Project/Area Number |
16590137
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General anatomy (including Histology/Embryology)
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| Research Institution | Tokyo Medical and Dental University |
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Principal Investigator |
AKITA Keiichi Tokyo Medical and Dental University, Graduate School, Unit of Clinical Anatomy, Associate Professor, 大学院医歯学総合研究科, 助教授 (80231819)
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| Project Period (FY) |
2004 – 2006
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| Keywords | cloaca / anorectal canal / external anal sphincter / programmed cell death / genital tubercle / pectinate line / pelvis |
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| Research Abstract |
The anorectal canal has two origins ; the upper part is derived from endoderm and the lower part is derived from ectoderm. The process of ectodermal contribution to the canal is remains unclear. To understand the development of this area, serial sagittal sections of mouse embryos were made every 12 hrs from embryonic day 13.0 (E13.0) to E18.5. Three-dimensional reconstructions were obtained from these sections. At the disappearance of the cloacal membrane (E13.5), endodermal lining reached the site of disintegrated membrane. Thus the whole canal had endodermal origin. The dorsal end of the primary perineum was thicker than other ectodermal epithelium, and in this transitional region it changed from an acute to obtuse angle. After it straightened out and formed the canal, the secondary perineum appeared caudally. During these processes, the external sphincter appeared in the underlying mesenchyme of the thick ectoderm, and functioned as a drawstring to form the ectodermal anal canal.
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