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Fig. 80. Diagrams representing hypothetical stages in the development of the human embryo

A, Morula; compare with Fig. 55, a.

B, Morula with differentiated superficial cells; compare with Fig- 55) b.

C, Central cells have become vacuolized to form the yolk cavity, leaving a small group (the inner cell mass) attached to the enveloping layer (trophoderm) ; compare with Fig- 5 5 , d.

D, Cells of the inner cell mass which are adjacent to the yolk cavity have become differentiated and have begun to grow around the cavity, forming the entoderm; compare with Fig. 59, a.


The series of diagrams in Figs. 80, 81 and 82 has been constructed to give the student a general idea of the changes that occur in the early stages of human development. It must be recognized, however, that the diagrams represent purely hypothetical stages up to the conditions shown in diagram B in Fig. 81 which corresponds roughly to the Bryce-Teacher embryo (Fig. 73) ; even in this diagram the extent of the mesoderm is much less than in the known human embryo. In Fig. 82 diagram A approximates the Peters embryo (Fig. 74), diagram D the von Spee embryo (Fig. 77). The history of the accessory structures which are shown in part will be considered in the chapter on "Foetal Membranes".


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Pages where the terms "Historic Textbook" and "Historic Embryology" appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms and interpretations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Reference

Bailey FR. and Miller AM. Text-Book of Embryology (1921) New York: William Wood and Co.



Cite this page: Hill, M.A. (2019, March 23) Embryology Bailey080.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Bailey080.jpg

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