Embryology stages Flashcards
1
Q
End of Week 1 milestones
A
Week 1: (cleavage mitosis w/no change in size of zona pellucida outer covering)
Day 2 - zygote
Day 3 - morula (32 cell)
Day 5 - blastocyst (blastulation - trophoblasts surround inner cell mass of embryoblasts on one side and blastocoel on other
Day 7 - implantation + bHCG secretion (no zona pellucida allows implantation)
2
Q
End of Week 2 milestones
A
Week 2: 2 weeks = 2 layers formed
Embryoblast –> Bilaminar disc (epiblast - fetus, hypoblast - dies)
3
Q
End of Week 3 milestones
A
Week 3: 3 weeks = 3 layers
a) Gastrulation: epiblast invaginates to form PRIMITIVE STREAK. Establishes ectoderm, mesoderm, endoderm. b) Neurulation - mesoderm becomes notochord --> then causes ectoderm on top to form neural plate. Neural plate folds to make neural groove, which folds more to make neural tube + some cells separate to form neural crest (PNS)
4
Q
End of week 4 milestones
A
Closure of neural tube (folic acid important)
