From Embryology

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Fig. 61. Sections of blastocysts of the white rat, showing inversion (entypy) of the germ layers


A, blastocyst 6 days and 14 hours after insemination.

B, blastocyst 8 days and 1 8 hours after insemination, with egg-cylinder cut longitudinally.

C, similar section of blastocyst 7 days and 22 hours after insemination (younger than B but further advanced in development), showing beginning of proamniotic cavity.

D, similar section of blastocyst 8 days after insemination (younger than B but further advanced in development), showing more advanced proamniotic cavity.


  1. Ectoplacental cone
  2. ectodermal node
  3. primary embryonic ectoderm
  4. extraembryonic ectoderm
  5. transitory ectoderm (original wall of blastocyst)
  6. proamniotic cavity
  7. visceral entoderm
  8. cells of parietal entoderm
  9. primary embryonic entoderm.

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Pages where the terms "Historic" (textbooks, papers, people, recommendations) 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, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)


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

Cite this page: Hill, M.A. (2024, April 13) Embryology Bailey061.jpg. Retrieved from

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