Embryology 2 Flashcards
What cells make the trophoblast
- Cytotrophoblast
- Syncytiotrophoblast
What do cytotrophoblast & syncytiotrophoblast help the trophoblast with
Implantation
What cells make the embryoblast
- Hypoblast
- Epiblast
Why doesn’t the mother’s immune system attack the blastocyst
- Syncytiotrophoblast release substances which hide it from IS
- Multinucleated cells formed
- No gaps for immune cells to get to embryo
What is the first stage of organisation of the body plan
Bilaminar formation
What is the significance of the bilaminar
- Bilinear
- Established dorsal & ventral axis
Why bilinear
Two embryoblast cells
Which cells form the ventral aspect of embryo
Hypoblasts
Which cells form the dorsal aspect of embryo
Epiblasts
How does amniotic cavity form
Small fluid-filled cavity in epiblasts
When does full implantation take place
Day 9
What happens in full implantation
- Migration of hypoblast cells encase blastocyst cavity
- Primary yolk sac forms
When does the coagulation plug form
Full implantation
What is the function of the coagulation plug
Protect blastocyst on uterine lining
How does embryoblast receive nutrients if no placental circulation happening yet
Diffusion of nutrients via uterine gland
How is the uteroplacental circulation established
Syncytiotrophoblast erodes walls of maternal capillaries
Where do the different cells receive their nutrients from
Trophoblastic lacuna
What is the extraembryonic mesoderm
Layer of connective tissue derived from yolk sac cells
When is extraembryonic mesoderm formed
Simultaneously with uteroplacental circulation
Days 10-11
Where is extraembryonic mesoderm formed
Between 1ry yolk sac & cytotrophoblast
When extraembryonic mesoderm is fully developed what does it cover
Amniotic cavity
When does blastocyst receive blood supply
When trophoblast breaks down the capillary wall
What forms and grows in the extraembryonic mesoderm
Chrionic cavity
When does chrionic cavity form
Days 12-13
When is 2ry (definitive) yolk sac formed
Days 12-13
How is the 2ry yolk sac formed
2nd wave of hypoblast cells migrating
Where are the amniotic cavity & 2ry yolk sac suspended
Chronic cavity by connecting stalk
What forms the bilamina disc
Embryonic sac & definitive yolk sac
What is the fate of the connecting stalk
Forms umbilical cord
What hormones do syncytiotrophoblast secrete
What is its function
What is it helpful for
Human chronic gonadotrophin - hCG
- Maintains endometrium
- Role in maternal immunotolerence
Pregnancy testing
How frequent is abnormal implantation sites
- 2% of pregnancies
- 9% of pregnancy-related deaths
What is placenta Previn
When placenta block vagina
What can placenta Persia cause
Severe bleeding in late pregnancy
Where do the majority of ectopic pregnancies happen
Uterine tube
How can abdominal implantation happen
Zygote entering the gap between ovary & uterine tube
When does lithopaedion occur
When abdominal pregnancy remains undiagnosed
How does baby die in lithopaedion
Too large to be reabsorbed —> calcifies
Why does foetus calcify in lithopaedion
Protect mother from its necrotic tissue
What is the hydatidiform mole
Development of trophoblast without embryonic tissue
What causes hydatidiform mole
Fertilisation of an empty egg
Explain parental imprinting in relation to hydatidiform mole
Parental genes favour formation of trophoblast at the expense of embryo
Why does hydatidiform mole still make you think someone is pregnant
Syncytiotrophoblast produces hCG —> +ve pregnancy test
