Placenta and Fetal Membranes Flashcards
what do the fetal membranes include?
chorion, amnion, umbilical vesicle, and the allantois
what is the fetal part of the placenta?
the chorionic sac (outermost fetal membrane)
what is the maternal part of the placenta?
derivative from endometrium
what connects the placental circulation with the fetal circulation?
vessels in the umbilical cord
What is the decidua?
the functional layers of the endometrium that separates from the remainder of the uterus after childbirth
what are the three parts of the decidua?
decidua basalis, decidua capsularis, decidua parietalis
what area of the decidua forms the maternal part of the placenta?
decidua basalis
what can the decidua capsularis be thought of as?
the chorion
what can the decidua parietalis be thought of as?
“walls” of the uterus
when does implantation typically occur?
late 2nd week (~ 10 days post-fertilization)
how do the trophoblast differentiation when implanting?
they differentiate into cytotrophblasts and syncytiotrophoblasts
which new layer of the blastocyst is responsible for invading and displacing the decimal cells of the endometrium?
the syncytiotrophoblasts
what eventually appears in the syncytiotrophoblast layer that allows for blood and uterine secretions to wash and bathe over the implanting embryo?
lacunae
what forms when adjacent lacunae fuse together?
lacunar networks
what is the primordial uteroplacental circulation?
it is where O2 and nutritive substances pass to the embryo via diffusion through lacunar networks
what is the chorionic sac made up of?
extra embryonic somatic mesoderm, cytotrophoblasts, and syncytiotrophoblasts
what is the thin tough membrane that surrounds the embryo/fetus and the amniotic fluid?
the amnion
how did the amnion develop?
from a population of cells known as amnioblasts (these separate from the epiblast and enclose the amniotic cavity)
what is the umbilical cord covered with?
the amnion forms an epithelial covering over the umbilical cord
what is amniotic fluid initially derived from?
maternal tissue and interstitial fluid; later fetal urinary, respiratory, and GI systems will also contribute
what is (poly)hydramnios?
excessive amniotic fluid; too much produced or not removed effectively
what could cause (poly)hydramnios?
genetic and/or CNS anomalies or blockage of the GI tube
what are the clinical signs of (poly)hydramnios?
abdominal pain, significant swelling or bloating, and breathlessness
what is a potential risk associated with (poly) hydramnios?
PROM (pre-mature rupture of membranes)
what is oligohydramnios?
insufficient amniotic fluid
what results from oligohydramnios?
renal agenesis, pulmonary hypoplasia, club footing; placental abnormality or maternal high blood pressure
what two things are critical for establishing the placenta?
formation of the villous chorion and the chorionic villi from the chorionic sac
where do the cytotrophobasts proliferate?
at the chorionic plate
after proliferating at the chorionic plate, what do the cytotrophoblasts do?
they extend through the syncytiotrophoblasts to attach to the decidua basalis
when extending through the syncytiotrophoblasts, where is the boundary for where the cytotrophoblasts will stop extending?
the cytotrophoblastic shell (surrounding the chorionic sac)
what does the extension of the cytotrophoblast/ cytotrophoblastic shell create and enclose?
the intervillous space (created from the lacunar networks)
what does decimal erosion produce?
placental septa
what does the placental septa divide the villous chorion into?
irregular convex areas known as cotyledons
when do the intervillous spaces start containing maternal blood?
11-14th week
when do the cytotrophoblasts grow into the syncytiotrophoblast layer?
end of week 2
when do the cytotrophoblasts form syncytial columns? (like little branches all along the chorionic sac)
through week 8
where would you expect to find the villi with the branches?
with the decidua basalis- form bushy area of the chorionic sac, the villous chorion
what is the smooth chorion?
the villi associated with the decidua capsularis become compressed and then degenerate
what is the structure of the primary villi?
cytotrophoblastic core covered by syncytiotrophoblasts
what is a secondary villi and when do you get it?
the extra embryonic mesoderm grows into the primary villi - 3rd week
what makes up the secondary villi?
extra embryonic mesoderm (core), cytotrophoblasts, and syncytiotrophoblasts
how do you get a tertiary villi?
the extra embryonic mesoderm differentiates into capillary and blood cells
what is the outer layer of the tertiary villi?
syncytiotrophoblasts
what is the middle layer of the tertiary villi?
cytotrophoblasts
what is the core of the tertiary villi?
capillaries and extra embryonic mesoderm
what are the two subpopulations of tertiary chorionic villi?
early and late (late tertiary chorionic villi start to lose the cytotrophoblastic layer
what is the main stem villi extending from?
the chorionic plate
what are the branch villi extending from?
the main stem villus
what is the anchoring villi?
villi that attaches to the maternal tissues through the cytotrophoblastic shell
what do cotyledons contain?
2 main stem villi and multiple branch villi
where does the main exchange between mother and fetus occur?
via the branch villi
what happens to the decidua capsularis are the embryo//fetus grows?
the capsularis will degenerate
what happens once the capsularis degenerates?
the amnion and the chorion will fuse
what do you get when you fuse the amnion and the chorion?
the amniochorionic membrane
what does the amniochorionic membrane fuse with on the opposite wall?
the decidua parietalis (it can now span the internal uterine os)
what things cannot cross the placenta?
protein hormones (pituitary hormones), bacteria, and drugs with amino-acid-like structures
what kind of tissue comprises the umbilical cord?
mucous tissue (Wharton’s jelly)
what are the contents of the umbilical cord?
two umbilical arteries and one umbilical vein, allantois
what do the umbilical arteries carry?
deoxygenated blood
what do the umbilical veins carry?
oxygenated blood
what is one of the most common umbilical cord anomalies?
absences of one umbilical artery
who is at risk for absence of one umbilical artery?
fetuses with chromosomal and fetal anomalies
what is the risk of absence of one umbilical artery?
it can impact perinatal and 3rd stage labor outcomes
what is placenta previa?
a condition where the placenta implants in the lower uterine segment or cervix
what does placenta previa often lead to?
serious 3rd trimester bleeding
what is placenta accrete/a?
partial or complete absence of the decidua–> so the villous chorion adheres directly to the myometrium
what is the result of placenta accrete/a?
failure of placental separation at birth
what is a hydatidiform mole?
a placental anomaly because of faulty fertilization; there is replacement of normal villi by dilated or hydronic (edematous) translucent vesicles
what are the two types of hydatidiform moles?
partial mole or complete mole
which mole does not have any fetal tissue?
compete mole
what happens in a case of a partial mole?
a normal ovum is fertilized with two sperm
what would the karyotype of a partial mole be?
triploid or tetraploid
what happens in a case of a complete mole?
there is fertilization of a blighted movum- all DNA is paternal; it is either fertilized by two sperm or there is duplication of a single sperm
what would the karytype of a complete mole be?
46 XX or 46XY
what is gestational trophoblastic disease?
a placental anomaly due to issues with invasion
what are invasive moles?
complete moles that penetrate or perforate the uterine wall
how are invasive moles diagnosed?
by persistent high blood levels of hCG
what are invasive moles responsive to?
chemotherapy
what is a gestational choriocarcinoma?
a highly invasive metastatic tumor that arises from trophoblast cells
what do monozygotic twins originate from?
one zygote
what are the membranes in monozygotic twins dependent upon?
timing of the division
if there is cleavage in the 2-8 cell stage (0-72 hours), what is the nature of the membranes?
diamniotic and dichorionic
if there is cleavage in the blastocyst stage (4-8 days) what is the nature of the membranes?
diamniotic and monochorionic
if there is cleavage in the implanted stage (9-12 days) what is the nature of the membranes?
mono amniotic and monochorionic
the earlier the split the…?
the more separate the membranes and the placenta will be
what do dizygotic twins originate from?
two zygotes
what do you get when you have separate implantation of 2 zygotes?
2 chorions and 2 amnions
what do you get when you have adjacent implantation of 2 zygotes?
2 amnions, 2 fused chorions, and 2 placentas
