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