File:Pohlman1911 plate1A.jpg

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Plate 1A

Model A Embryo No. 3 (Mall No. 164; 3.5 mm. ; + ; 20; Good). x 100. Cloaca well developed and limited for caudal half of the ventral border by epithelial cloacal membrane. Allantois comes off at right angles and at lower border of dermal navel. Lateral furrow along later line of division. Carnegie stage 11

This model shows the cloaca to be a sort of conical sac receiving the wider lumened hind gut dorsally, and the narrow lumened allantois ventrally. The latter joining the cloaca at about a right angle. The cloaca is much wider dorsally and is somewhat wedged-shaped in section. Ventrally, it is limited for about one-half of its extent by the epithelial cloacal membrane which is indicated by a surface contact. The right wall of the cloaca is concaved from before backwards while the left side (shown) is correspondingly convex, and presents a well marked furrow extending from the saddle between the allantois and hind gut to about the mid area of the cloacal membrane. This furrow is interesting because while it indicates the probable line of the later division, it was found in but two embryos of the series examined. The part of the cloaca caudal to the cloacal membrane "the tail gut" is quite short and cone-shaped. The model with the exception of the furrow conforms to Keibel's model of the His embryo EB (3 mm.)

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


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 plate1A.jpg. Retrieved from

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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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