Developmental Anatomy
Stage 5: Lab Manual - Horizon 5 Ovum Implanted But Avillous
- 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?
- 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?
- 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.
Developmental Stages in Human Embryos by Ronan O'Rahilly and Fabiola Müller.
Published by Carnegie Institution of Washington, Publication 637. 1987.
Stage 5 (PDF 686 KB)
QUESTION: What fills the intercommunicating lacunar spaces?