Paper - The prechordal plate in a human embryo with small neuropore

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Atwell WJ. The prechordal plate in a human embryo with small neuropore. (1926) Anat. Rec. 32(3):200.

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This historic 1926 paper by Atwell described development of the prechordal plate in a human embryo with small neuropore. The author identifies this embryo by comparison with other embryos as a Carnegie stage 11

See also by this author Atwell WJ. The development of the hypophysis cerebri in man, with special reference to the pars tuberalis. (1926) Amer. J Anat. 37: 139-193.

Carnegie Collection

Carnegie Collection - Stage 11 
Serial No. Pairs of somites Size (mm) Grade Fixative Embedding Medium Plane Thinness (µm) Stain Year Notes
470 17 E, 4.3 Ch, 16 Good Formol P Transverse 10 Al. carm. . 1910

Carnegie Collection - Stage 11 
Serial No. Pairs of somites Size (mm) Grade Fixative Embedding Medium Plane Thinness (µm) Stain Year Notes
2053 20 E, 3.1 Ch, 12 Exc. Formol P Transverse 10 Al. coch. 1918 Most advanced in group. Ag added to slide 2
Monographs by Davis (1923)[1] and Congdon (1922)[2]
  • Size - E. is the greatest length of the embryo and Ch. is the mean diameter of the chorion.
  • Grade - total grade of the specimen and includes both its original quality and the condition of the mounted sections.
  • Embedding medium - paraffin (P) or a combination of celloidin and paraffin (C-P).
  • Fixative - formalin (Formol), alcohol and formalin (Alc, formol), Bouin (Bouin solution)
  • ? - unknown or not determined.

Modern Notes

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Search PubMed - prechordal plate

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The Prechordal Plate in a Human Embryo with Small Neuropore


Wayne J. Atwell

Department of Anatomy, University of Buffalo.

Abstract of paper presented at the Forty-Second Annual Session American Association of Anatomists, Yale University, New Haven, Connecticut April 1 to 3, 1926.

The embryo (no. 52, U.B.E.C., no. 5072, Carnegie Collection) was obtained at an operation for tuba1 pregnancy. Thirteen pairs of somites are distinctly separated and four more pairs are indicated by slight constrictions. In many respects the embryo is intermediate between no. 470 of the Carnegie Collection and no. 2053, described by Davis. The neuropore is present, but very small. The pharyngeal membrane is not perforated, although changes in the epithelium indicate places at which perforation is to occur. Communication of the yolk sac with the gut is wider than the Davis embro; more so even than in no. 470. The dorsal flexure is well marked, but the curves are gentle and do not necessitate considering the bending as due to artifact. The atrial portion of the heart has not risen up dorsal to the bulbar portion. The first pair of aortic arches is complete, while the second pair is in an early stage of formation.

At the cephalic end of the notochord is a structure which is probably to be interpreted as a rudimentary prechordal plate. The lateral extensions are not so extensive as in the embryo with seven pairs of somites described by Payne. The structure bends around the cephalic end of the foregut and for a large part of its length is free of attachment to either ectoderm or entoderm.

Cite this page: Hill, M.A. (2024, June 23) Embryology Paper - The prechordal plate in a human embryo with small neuropore. Retrieved from

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