Bilaminer Disc & Endometrium Implantation Flashcards
Week 2
Bilaminer disc and endometrium implantation
Review of blastula
- Day 5
- hallow ball of cells
- Morula (SOILD ball) becomes Blastula (HALLOW ball)
- Rapid series of mitotic cell divisions results in daughter Blastomeres
- By Day 6: About 100 cells
- AKA: Blastoderm or blastodisc around a space called the Blastocoel
ICM: embryo
Trophoblast: placenta
What is the purpose of the Bilaminer Disc?
- Need to set up the organization of the embryo and extraembryonic membranes
- prep for implantation into uterus
- ICM (embryoblast) gives rise to 2 layered structures (epiblast and hypoblast)
- these two layers together are flanked by the amniotic cavity and yolk sac
What are the two layered structures the embryoblast gives rise to?
1.) Epiblast
2.) Hypoblast
ICM is also called
- Bilaminer disc
- the primitive endoderm
4 extraembryonic membranes
- protect and manage nutrients and wastes:
1.) Chorion– vessels
2.) Amnion– sac and fluids
3.) Allantois– wastes
4.) Yolk sac– nutrients
Waste removal is taken over by the______
umbilical cord
Movement of cells and cavities
cells need to differentiate and replicate
ICM called the _________
Bilaminer disc
ICM differentiates further into
1.) Epiblast (dorsal)
2.) Hypoblast (ventral)
Bilaminer disc forms
- embryo proper (fetus)
- extraembryonic membranes
The bilaminer disc splits the sphere to make TWO cavities
1.) Amniotic
2.) Chorionic/Blastocyst
ICM into Epiblast into what?
- into the 3 germ layers
- Allantois
- Amnion
ICM into Hypoblast into what?
- into Chorion
- Yolk sac
- does NOT become embryo
Amniotic cavity develops between__________ and __________
Trophoblast; Epiblast
Amniotic cavity
a thin layer of cells from epiblast surrounds the amniotic cavity to become the AMNION
Syncytio-tropho-blast (STB) (together-nourish-cells)
- the outer syncytial layer of the trophoblast that actively invades the uterine wall forming the outermost fetal component of the placenta
- *Nutrient and waste exchange
- Hormone synthesis
- *STB produces human chorionic gonadotropin (hCG), a hormone that stimulates the corpus luteum to produce progesterone, which helps maintain the pregnancy
- *Protein and lipid metabolism
- *Anti-angiogenic factors
- *In preeclampsia, a major cause of maternal mortality and morbidity, the release of syncytial factors increases
Cyto-tropho-blast (cells-nourish-cells)
- a tissue of specialized cells in the placenta that lines the cavity and extends into the syncytiotrophoblast
- *Invade the uterus and replace maternal cells that line uterine vessels; this allows them to divert maternal blood to the placenta
- give rise to the plasmodial syncytiotrophoblast, which covers the placental villi *“Development”
- *highly metabolically active and contribute to global metabolism in the placenta
- *generate lipid droplets containing triglycerides and other lipid species
- *also involved in preeclampsia- associated with shallow cytotrophoblast invasion, which can lead to decreased blood flow to the fetus
The hypoblast cell number increases from Day 8-12
Hypoblast cells sends out 2 waves of endodermal cells into blastocoel
1st wave
makes primary yolk sac
2nd wave
transforms 1 degree yolk sac into a 2 degree yolk sac
Chorion cavity
develops between trophoblast, outer amnion, and yolk sac from new extraembryonic mesodermal cells
On days 11-13
Mother’s blood vessels move in
Mammal gastrulation is similar to_____
birds
The embryo is now a germ disc with:
- upper layer epiblast
- lower layer hypoblast
ICM epiblast delaminates, forming what?
1.) Amniotic cavity
2.) Amnion
3.) Amnionic cavity (at embryonic pole)
Hypoblast forms what?
1.) Yolk sac
2.) Chorion
Epiblast cells will migrate through a _________ ________ forming embryonic primitive ________ and _________
Primitive Streak; Endoderm; Mesoderm
