34 Placenta Flashcards
Maternal component of placenta =
DECIDUA = new name stratum functionalis of endometrium
– shed at birth
Functional portion of maternal placenta =
Decidua Basalis
Fetal portion of placenta =
CHORION – from trophoblast and its two layers (cryptoblast/syncytiotrophoblast) with some extraembryonic mesoderm
Functional portion of fetal placenta =
Villous Chorion
At implantation the TROPHOBLAST invades endometrium and differentiates into two layers
CYTOtrophoblast and SYNCTIOtrophoblast
This layer is dervived from the cytotrophoblast and secretes HCG
Is the layer thats in Direct contact with maternal blood
SYNCTIOtrophoblast
this structure projects into lacuna with maternal blood – day 13
CHORIONIC VILLI – primary villi
Days 19-20 the cytotrophoblast forms an outer shell attached to the uterus. Maternal blood pierces the shell to flow in and out of _____
intervillous spaces = former lacunae
This forms when the mesenchyme (CT) enters the core of the villi
Secondary Villi
when fetal capillaries form in the mesenchyme of the villi, they become
Tertiary Villi
When does the heart begin to beat/uteroplacental circulation becomes functional
4th Week
how does highly oxygenated blood return to the fetus from the placental
via the UMBILICAL VEIN
poorly oxygenated blood is sent from the fetus back to the placenta via
umbilical arteries
highly oxygenated blood enters the intervillous spaces from endometrial arteries into what space in the endometrium
Decidua basalis
how does poorly oxygenated blood in the intervillous space exit the placcenta
Via the endometrial veins
What prevents maternal blood from mixing directly with fetal blood
Placental Barrier
gestational trophoblastic disease – rare tumors derived from uncontrolled trophoblast cells
most common are benign =
HYADTIDIFORM MOLES
pregnancies without an embryo
two eggs are ovulated by and fertilized by TWO different sperm forming two zygotes
DIZYGOTIC = fraternal twins
ONE egg is fertilized by ONE sperm forming ONe zygote which later splits into two embryos
MONOZYGOTIC = identical twins
if zygote splits at 2 cell stage through morula stage
DICHORIONIC/Diamniotic – each embryo will have its own amnion and chorion
if zygote splits at blastocyst stage –>
Monochroionic/Diamniotic = 2 seperate amnions and one chorion
if the zygote splits after implantation when the bilaminar disc and amnion have formed
MONOchorionic and MONOamniotic
if the embryo splits during or after the primitive streak has formed –>
then the embryos will only partially separate leading to conjoined twins with a shared amnion and chorion – rare
