File:Johnson1914 plate06.jpg

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Fig. 20 Side view of reconstruction of the epithelium of the pars analis recti of an embryo of 240 mm

X 6.

A model of the pars analis recti of an embryo of 240 mm is represented in figures 19 and 20. The ampulla is shown above as cut off at a point where it has about reached its greatest width. It is separated from the bulbiis analis by a constricted zone which, as determined from the sections of this series, lies a little above the ano-rectal line. This portion of the rectum (ampulla) presents only intestinal glands, villi having entirely disappeared. Owing, however, to the difficulty met with in modeling the glands at the magnification used (24 diameters) no attempt has been made to represent them. All the folds of the pars analis recti have been modelled. The primary folds can be best seen in cross sections of this region but they are distinguishable in the model. The posterior, right, and left primary outfoldings are present as in the youngest stages, and the left, as seen in the figures, passes down onto the aiitcrioi' hordci' of the fhittciKHl zona intermedia. The posterior i-iinai'y fold passes into the posterior border of the same, while the right fold terminates on the side of the zona intermedia. The secondary folds are more numerous than in the above described stages. Of these there are about twelve on the left primary fold, twenty-two on the right, and about twenty-six on the left, about sixty in all.


Johnson FP. The development of the rectum in the human embryo. (1914) Amer. J Anat. 16(1): 1-58.

Cite this page: Hill, M.A. (2024, February 22) Embryology Johnson1914 plate06.jpg. Retrieved from

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