Week 2 of development Flashcards
The trophoblast differentiates into ____________ (1)and _____________(2).
The embryoblast differentiates into the ___________ (3) and ___________.(4)
- Cytotrophoblast
- Synctiotrophoblast
- Epiblast
- Hypoblast
When is the bilaminar disc formed?
When the blastocyst implants
Day 8
Describe the cytotrophoblast
It is the inner layer
It forms mononuclear cells that migrate into the synctiotrophoblast.
Describe the synctiotrophoblast
It is the outer layer
-It is a multinuclear mass that is expanding rapidly, and as an irregular shape
-Unable to clearly view cell boundaries
Endometrial cells undergo ___________ to facilitate implantation
apoptosis
What regulates trophoblast fusion?
Cyclic Adenosine Monophosphate AMP (cyclic AMP) pathway
What happens to the connective tissue surrounding the implantation site?
Connective tissue surrounding implantation site begins to
degenerate adjacent to the synctiotrophoblast.
How does the blastocyst get nutrition?
The synctiotrophoblast engulfs the endometrial cells that died due to apoptosis. That is how it nourishes itself
What are lacunae?
Irregular spaces in the synctiotrophoblast which fuse. The fused spaces are called lacunae.
What is the function of the lacunae in the synctiotrophoblast?
The trophoblastic lacunae fuse to form an intercommunicating network which communicates with maternal capillaries (sinusoids) as the synctiotrophoblast penetrates the endometrium further.
Name the usual implantation site
Superior part of the body of the uterus
- More often on the posterior wall than the anterior wall.
Define ectopic pregnancy
Implantation outside the uterus
State the 4 sites of ectopic pregnancy
Tubal (most common) – in the uterine tubes
▪ Ovarian (least common) – at the ovary
▪ Abdominal – in the mesentry of the abdomen
▪ Cervical – sometimes included as uterine pregnancy but is considered ectopic
What hormone does a pregnancy test detect? and what structure releases this hormone?
*HCG (Human chorionic gonadotrophin) produced by synctiotrophoblast enters
maternal blood in lacunae and is the basis of pregnancy tests
Describe what placenta previa is.
Placenta previa is when the placenta partially or completely covers the opening of the cervix.
-It is caused by the implantation of the blastocyst on the inferior part of the uterus.
-This may cause bleeding due to the premature separation of the placenta during pregnancy or at the time of delivery.
What hormones are in the morning after pill?
progestins/anti-progestins - they affect implantation
How can intrauterine devices disturb implantation?
-They can cause a local inflammatory reaction to disturb implantation
- in some cases the device contains slow releasing
progesterone to disrupt endometrial development.
When is the bilaminar disc formed?
Approximately day 8
Describe the two layers of the bilaminar disc
A distinct external layer of columnar cells – EPIBLAST
▪ Adjacent to the amniotic cavity
- An internal layer of cuboidal cells – HYPOBLAST
▪ Adjacent to the blastocyst cavity.
How is the dorsal-ventral axis of the blastocyst defined?
Hypoblast - ventral
Epiblast - dorsal
Describe amnion and amniotic cavity formation
Implantation progresses – fluid-filled space appears in
embryoblast
- Space is the primordium for Amniotic Cavity
* Amnioblasts separate from epiblast forming AMNION
which encloses Amniotic Cavity
_____________ forms floor of the amniotic cavity, and continues peripherally with amnion
Epiblast
When does the formation of amniotic cavity occur?
Around day 8 - it forms together with the bilaminar disc.
What forms the roof of the exocoelomic membrane?
Hypoblast
