File:Pohlman1911 plate2C.jpg

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Plate 2C

Model C

This model shows marked degeneration of the tail gut. The allantois is narrow lumened, while the widely lumened ventral cloacal segment lies ventral to the hind gut and dorsal segment, and is separated from them by peritoneum. The Wolffian ducts open in the same situation as in the foregoing model, and present dorsal diverticulae, the renal buds. The ventral portion of the cloaca, especially the area above the cloacal membrane, is markedly widened and flattened. The lateral furrow of Model A was not present. This model conforms to the Keibel model of a 6.5 mm. embryo (a considerably older stage if we go by the greatest length rule). The cloaca has lost its more or less even width and attains its greatest lateral diameter at the level of the Wolffian orifices. There is no evidence of displacement of the Wolffian ducts from their primitive position in relation with the upper limit of the cloacal membrane.

Embryo No. 9 (Mall 80; 5.0 mm; + ; 10; Good). Model C. x 100. About the same as the foregoing stage. Tail gut undergoing degenerative changes. Carnegie stage 14


Key to Lettering

A., Allantois

K., Kidney

A.M., Position of anal membrane

P.T., Precloacal mesodermic tissue

C., Cloaca

R.B., Renal bud

CM., Cloacal membrane

T.G., Tail cut

C.S., Cloacal segment of Wolffian duct

U., Ureter

G.E., Genital eminence

U.G., Urogenital sinus

H.G., Hind gut

U.M., Position of urogenital membrane

* Probable position of point where allantois joins cloaca.

All drawings represent 100 diameters enlargement except of Model F which is 50 diameters.

Links: plate 1 | 1 A | 1 B | plate 2 | plate 2C | plate 2D | plate 3 | plate 3E | plate 3F | Pohlman 1911

Reference

Pohlman AG. The development of the cloaca in human embryos. (1911) Amer. J Anat. 12: 1-26.


Cite this page: Hill, M.A. (2024, February 23) Embryology Pohlman1911 plate2C.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Pohlman1911_plate2C.jpg

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G

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