Lecture 11 - Placenta I

Question 1

Preeclampsia?

Answer 1

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

Question 2

Essential functions of the placenta?

Answer 2

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

Question 3

Placenta and blood systems?

Answer 3

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

Question 4

Implantation? (not important)

Answer 4

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

Question 5

Humans are inferitle?

Answer 5

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

Question 6

Placenta formation (day 12)?

Answer 6

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

Question 7

Placenta formation (day 14)?

Answer 7

extraembryonic mesenchyme invade primary villi forming secondary villi

Question 8

Placenta formation (day 18-20)

Answer 8

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

Question 9

Floating Villi?

Answer 9

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

Question 10

Chorion Lavae?

Answer 10

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

Question 11

Chorion Frondosum?

Answer 11

villi at the base of the implantation site

Question 12

Regressing villi on a 7.5 week placenta?

Answer 12

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

Question 13

Anchoring villi?

Answer 13

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

Question 14

Endovascular trophoblasts?

Answer 14

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

Question 15

Causes of inadequate growth?

Answer 15

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

Question 16

Consequences of intrauterine growth restriction? (IUGR)

Answer 16

increased likelihood of premature and stillbirth

Question 17

Endovascular trophoblast plugs?

Answer 17

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