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Week 8 Human Embryo

Tail end of human embryo, from eight and a half to nine weeks old

(From model by Keibel.)

The entodermal cloaca is divided into a dorsal and a ventral part by means of a partition, the urorectal septum (Fig. 992), which grows downward from the ridge separating the allantoic from the cloacal opening of the intestine and ultimately fuses with the cloacal membrane and divides it into an anal and a urogenital part. The dorsal part of the cloaca forms the rectum, and the anterior part of the urogenital sinus and bladder. For a time a communication named the cloacal duct exists between the two parts of the cloaca below the urorectal septum; this duct occasionally persists as a passage between the rectum and urethra. The anal canal is formed by an invagination of the ectoderm behind the urorectal septum. This invagination is termed the proctodeum, and it meets with the entoderm of the hind-gut and forms with it the anal membrane. By the absorption of this membrane the anal canal becomes continuous with the rectum (Fig. 993).



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Reference

Gray H. Anatomy of the human body. (1918) Philadelphia: Lea & Febiger.


Cite this page: Hill, M.A. (2024, June 17) Embryology Gray0993.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Gray0993.jpg

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current16:01, 28 April 2011Thumbnail for version as of 16:01, 28 April 2011600 × 545 (88 KB)MarkHill (talk | contribs)==Week 8 Human Embryo== Tail end of human embryo, from eight and a half to nine weeks old (From model by Keibel.) The entodermal cloaca is divided into a dorsal and a ventral part by means of a partition, the urorectal septum (Fig. 992), which grows

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