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  Lab Manual - Horizon 5 Ovum Implanted But Avillous
1st view 2nd view
  Stereo View
  • 0.1 - 0.2 mm
  • Solid synctio and cytotrophoblast without lacunar development
  • Amniotic cavity
  • A simple bilaminar germ disc
  • Early mesoblast formation
  • Ovulation age: 7 days

Question: True or False? In stage five the ovum is a complex bilaminar germ disc?

Horizon 5b
1st view 2nd view
Stereo View  
  • Synctiotrophoblastic lacunae with early utero-placental circulation
  • Amniogenesis
  • A simple bilaminar germ disc
  • Variable degrees of exocoelomic (Heuser's) membrane formation
  • Age: 9 days

Question: What is the state of utero-placental circulation in this 5b stage embryo?

Horizon 5c
1st view 2nd view
3rd view  
  • Intercommunicating lacunar spaces filled with maternal plasma containing increasing numbers of blood cells.
  • A distended chronic cavity of maximum size.
  • A bilaminar germ disc with no axis.
  • A well defined amnion and amniotic cavity.
  • The endometrial epithelium is proliferating to repair the penetration defect. From this defect created by the ovum arises a coagulum which communicates with maternal blood within the lacunae.
  • Ovulation age: 11 days

Question: What fills the intercommunicating lacunar spaces?

cover  

Developmental Stages in Human Embryos by Ronan O'Rahilly and Fabiola Müller.  Published by Carnegie Institution of Washington, Publication 637. 1987.

Stage 5 (PDF)
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