Lecture 11 - Placenta I Flashcards Preview

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Flashcards in Lecture 11 - Placenta I Deck (17):


hypertension specific to second half of human pregnancy (3-8%)


Essential functions of the placenta?

self maintenance/renewal, exchange/transport, separation, protection from maternal infections, protection from maternal immune system


Placenta and blood systems?

maternal and fetal blood systems do not mix, the placenta brings them into close apposition


Implantation? (not important)

inner cell mass of trophoblast attaches to endothelium of uterine wall, release enzymes that eat the wall, digests a hole that embryo moves into, after 4-5 days embryo is buried entirely inside wall of uterus


Humans are inferitle?

70% of conceptions lost (30 implantation, 30 early pregnancy, 10 miscarriage)


Placenta formation (day 12)?

cytotrophoblasts proliferate and invade trabeculae, becoming primary villi, lacunar system now called intervillous space


Placenta formation (day 14)?

extraembryonic mesenchyme invade primary villi forming secondary villi


Placenta formation (day 18-20)

capillaries form in villi (tertiary villi), from this point most villi are tertiary, vessels in villi connect to umbilical vessels carrying blood to and from fetus


Floating Villi?

most villi do not have contact with maternal tissue and float in intervillous space, these flaoting villi are responsible for the exhange and barrier functions of the placenta


Chorion Lavae?

compose of the villi to the sides and towards uterine lumen as the fetus is encapsulated by villi


Chorion Frondosum?

villi at the base of the implantation site


Regressing villi on a 7.5 week placenta?

placenta is originally a sphere surrounding the embryo, as gestation progresses, chorion lavae (sides and luminal) form smooth chorion, and chorion frondosum (basal to implantation site) remain as definitive placenta


Anchoring villi?

in these villi, cytotrophoblasts break through syncytiotrophoblast and spread laterally around the implantation site forming a cytotrophoblast shell, this shell remains in contact with maternal tissue through gestation - columns of cytotrophoblasts invade decidua and spiral arteries from anchoring villi during 1st and 2nd trimester


Endovascular trophoblasts?

extravillous trophoblast columns invade maternal spiral arteries an replace the endothelial wall, removing their smooth muscle also


Causes of inadequate growth?

inadequate depth of trophoblast invasion, and reduced number of vessels transformed


Consequences of intrauterine growth restriction? (IUGR)

increased likelihood of premature and stillbirth


Endovascular trophoblast plugs?

form during trophoblast infiltration of spiral arteries, lowers oxygen supply to early embryo, protects from over-supply of pulsatile blood, filter for plasma to pass without RBC