Implantation and Germ Layer Flashcards
What is the timeline for transport of developing embryo down the oviduct to uterus?
Six days. By the end of day one:2 cell stage Day 3: morula is in isthmus and corona radiata is lost Day 4: blastocyst is in the uterus Day 5: loss of zona pellucida Day 6: implantation
Blastocyst hatching?
Q
Major function of ZP.
Surrounds developing embryo until it reaches uterus.
What are the stages of implantation?
- Attachment of expanded blastocyst to endometrial epithelium
- Penetration of uterine epithelium
- Invasion into tissues underlying epithelium
- Erosion of maternal vascular supply
Decidual reaction and importance?
Decidual reaction is the response of endometrial stromal cells to the invading blastocyst. Decidual cells are derived from endometrial stromatolites cells that accumulate glycogen and lipid droplets.This results in massive cellular matrix that surrounds embryo and fills most of endometrium.
Provide immunologically privileged site to protect developing embryo from being rejected.
Ectopic pregnancies and where does it commonly occur?
Most commonly found in the Ampulla of the Fallopian tube, where fertilization occurs. >50%
Next most common occur in the isthmus ~25%
Third occurs in fimbriae ~17%
When does gastrulation begin?
At the end of the second week of gestation.
Two-germ layer stage: consists of epiblast and hypoblast.
What is the role of nanog and Gata6 in establishment of epiblast and hypoblast?
Nanog is expressed in the ICM in cells that enter early and these cells are then destined to become epiblast cells.
Gata6 is expressed when cells enter the ICM later and are destined to become hypoblast cells.
*Gata6 is induced by FGF-4
Difference between primary and secondary yolk sac?
Q
Formation of primitive streak?
Cell goes through cleavage to form the ICM, which then forms the Epiblast (and hypoblast). The epiblast then forms the embryonic epiblast (and amniotic ectoderm). Epiblast forms primitive streak.
What roles might Wnt and TGF-B play in formation of primitive streak?
TGF-B and Wnt could possibly induce the primitive node and streak.
What is induction?
Induction is
What is the significance of primitive groove and primitive node?
A
What are three classical molecular markers expressed by nodal cells?
A
What are bottle cells and what role do they play in gastrulation?
They extend themselves. Through the layer of epiblast into the space btw epiblast and hypoblast. They become mesenchymal cells that will become part of the mesodermal germ layer.
How does the expanded blastocyst attach to endometrial epithelium? (1st step in implantation)
Integrins are expressed by endometrium and trophoblast cells facilitate the attachment. The initial contact is between endometrial surface and embryonic pole of blastocyst.
How does penetration of the Uterine Epithelium and Invasion into underlying epithelium occur?
Syncytiotrophoblast projections penetrate the endometrial basal laminators and invade the stream. Trophoblastic lacunae appear and eroded endometrial blood vessels fill the lacunae with maternal blood and the trophoblast is less invasive.
What is the syncytiotrophoblast?
Cells lose individual identity the cell membrane fuse together. This is closest to the endometrium.
When is the worst time during pregnancy for introduction to teratogens?
First four weeks
What week of gestation do the germ layers form, and from what layer?
Form during third week of gestation from the epiblast.
What happens after blastulation?
Gastrulation, where the embryonic germ layers form.
What Transcription factor is related with epithelial mesenchymal cell transformation?
Snail
