01-29: Germ Layer Formation Flashcards
What is the most important event that takes place in fertilization?
the checking of degenerative changes occurring in the egg and the activation of protein synthetic mechanisms
**Necessary to produce the various proteins needed for subsequent events in embryogenesis
What is produced during blastulation?
the blastomeres usually separate to produce a temporary internal cavity which will allow some cells to acquire an internal position
What is the most important event in gastrulation?
morphogenetic movement
What is morphogenetic movement?
cells are arranged and brought closer together in some instances so that inductive interactions can occur
What is a secondary consequence of gastrulation?
the development of a 3-germ layer embryo (triploblasty)
What also occurs during gastrulation?
differentiation begins
What do bottle cells demonstrate?
active cellular movement during gastrulation (not passive)
What 2 cell layers are derived from the ICM during the 2-cell stage?
- Epiblast
- Hypoblast
When does gastrulation occur?
end of 2nd week of gestation
What are the 3 embryonic germ layers formed during gastrulation?
- Ectoderm
- Mesoderm
- Endoderm
Cells that enter the ICM at the earliest stage express ________ and are destined to become Epiblast cells
Nanog
Cells that enter the iCM at a later stage express ________ and are destined to become Hypoblast cells
Gata 6
What induces Gata 6 expression?
FGF-4 secretion from earlier cells
What are the 3 classical molecular markers expressed by nodal cells?
- chrodin
- goosecoid
- hepatic nuclear factor-3b (Foxa-2)
What does HA do in gastrulation?
- secreted into the space between the ecto and endoderm
- keeps mesoderm cells from aggregating too soon
