YAN PLACENTA Flashcards
(23 cards)
Describe the structure of a blastocyst.
inner cell mass=embryoblast
outer cell mass=trophoblast
blastocyst cavity
What happens to the blastocyst at day 6?
it implants in the endometrium! the outer trophoblastic cells invade the uterine epithelium/endometrial layer!
What happens to the blastocyst’s trophoblast by day 8?
it has 2 separate layers!
Outer layer = syncytiotrophoblast
inner layer = cytotrophoblast
What are other important features of the blastocyst on day 8?
amniotic cavity present
amnioblasts are there
epiblast & hypoblast are there too.
What happens to the trophoblast of the blastocyst on day 9?
you see the presence of trophoblastic lacunae
How did lacunae form in the trophoblast?
first you have vacuoles that form & then they fuse to form lacunae
What are other important features of the blastocyst on day 9?
primitive yolk sac
fibrin coagulum: closes everything off
What happens to the trophoblast around days 11-12?
uteroplacental circulation is established
**trophoblast lacunae become continuous w/ the maternal sinusoids. Therefore, maternal blood can enter circulation.
What are other features of the kid on days 11-12?
extraembryonic coelom
extraembryonic somatic mesoderm
extraembryonic splanchnic mesoderm
What happens to the trophoblast of the kid around day 13?
its cytotrophoblastic cell layer proliferates. It penetrates into the syncytioctrophoblastic layer. these become cellular columns & then primary villi.
What are other features of the kid @ day 13?
secondary yolk sac formed
connecting stalk
Describe the structure of a primary villus.
syncytiotrophoblast on the outside
cytotrophoblast on the inside
Describe the structure of a secondary villus.
syncytiotrophoblast on the outside
cytotrophoblast on the inside
**mesoderm core
Describe the structure of a tertiary villus or placental villus.
syncytiotrophoblast on the outside
cytotrophoblast on the inside
mesoderm core
**some of the mesoderm has become blood vessels & blood cells
What happens at the end of the 3rd week to the trophoblast?
maternal vessels find their way into the intervillous spaces, forms syncytium
Note: capillaries in the mesodermal core of the villi are connected to chorionic plate, then the connecting stalk, & then the intraembyronic vessels
**radial apperance b/c of the tertiary & secondary villi
What can you see on the fetal side of a full term placenta?
umbilical cord
amnion
chorionic plate w/ chorionic vessels
What is the rate of twin conceptions?
about 1/90
What percentage of twins are identical or monozygotic? What percentage of twins are fraternal or dizygotic?
Monozygotic: 30%
Dizygotic: 70%
What are the 2 main variations that you see with dizygotic twins?
whether they share the same placenta (fused)
or have completely separate placentas
What are the different variations that you see with monozygotic twins?
completely separate placentas
fused common shared placenta
shared placenta & common amniotic cavity
What are the 4 main functions of the placenta?
exchange of gases
exchange of nutrients & electrolytes
transmission of maternal antibodies
hormone production
What is the advantage of having transmission of maternal antibodies to the fetus?
gain of passive immunity
Where are the hormones produced in the placenta? Which hormones are produced?
syncytiotrophoblast
progesterones, estrogens, hCG, somatomammotropin (placental lactogen)
