Placental Development Flashcards
End of 1st week
blastocyst superficially implanted
2nd week- Extraembryonic mesoderm created by hypoblast cells
Extraembryonic mesoderm is now chorionic plate)
13 Day
Trophoblastic lacunae present @ embryonic & abembryonic pole
Uteroplacental circulation begun
2nd yolk sac lined by endoderm
Villi
formed by syncytium
Rests on a layer of cytotrophoblastic cells that cover core of villi
Cap sys developing in core of villi soon comes in contact w/ capillaries of chorionic plate & connecting stalk
Gives rise to extraembryonic vascular sys
Beginning week 3
Week 9
Nutrient demand increase
Increase surface area b/t maternal & fetal placenta
intrervillous spaces are lined by syncytium
Cytotrophoblastic cells surround trophoblast & entirely in contact with endometrium
Suspended by connecting stalk
Cytotrophoblast shell completely surrounds chorionic sac
- Protective & attaches chorionic sac tightly w/ decidual
Chorion Frondosum & laeve
Villi on embryonic pole continue to grow & expand- frondosum
Villi on abembryonic pole degen & by month 3= chorion laeve
Cytotrophoblast
In week 4, endovascular invasion by cytotrophoblst
Cytotrophoblast epithelial to endothelial transformation during month 4
Preeclampsia
maternal hyperT & proteinuria due to reduced organ perfusion
May progress to eclampsia w/ seizure
Reversible by baby delivery
Trophoblast disorder where cytotrophoblasts don’t diff and don’t undergo epith to endothelial transformation
Invasion of maternal BVs by these cells is rudimentary
Placenta components
Decidua basalis = maternal
Chorion frondosum = fetal
Amniotic fluid
Dispositon of fetal mem due to increased production of amniotic fluid
10 weeks= 30 mL; 20 wks= 450 mL; 37 wks= 1000 mL
End of 3rd month
amnion has expanded so that it comes in contact with chorion
Fusion of amnion & chorion to form the amniochorionic mem obliterating chorionic cavity
This mem ruptures during labor (breaking of H2O)
Yolk sac then usually shrinks & gradually obliterated
Umbilical Cord
week 5- primitive umbilical ring
week 10- primitive umbilical cord
2 arteries in blue & 1 vein in red (fetal reversed circulation)
Placenta in 2nd half of pregnancy
months 4 & 5- decidual septa project into intervillous space but do not reach chorionic plate
Decidual speta have core of maternal tissue & covered by syncytial layer, which separate maternal blood from fetal tissue of villi
Decidual septa divide placenta into cotyledons (compartments)
Placenta growth // to uterus. Covers up to 30% of internal surface of uterus
Increase in thickness of placenta due to arborization of villi.
Full term placenta
Torn from uterine wall at birth
Expelled from uterine cavity as afterbirth
Circulation of Placenta
maternal blood goes into intervillious space
80-100 spiral endometrial a. in pulsatile manner spurts maternal blood toward chorionic plate
As P dissipates, blood flows slowly over branch villi to allow gas exhange, nutrient & metabolic products
Blood returns through endometrial v. to maternal circulation
A red of circulation can result in fetal death
Placenta mem/barrier
Separates maternal & fetal blood
Endothelial lining
CT
cytotrophoblast
syncytium
@ month 4= thins into 2 layers (endothelial & syncytium)
Normally no mixing!
Erythroblastosis & Fetal Hydrops
when some fetal blood cells escape across placental barrier, can elicit Y response by mom
If mom response is sufficient- Y will attack & hemolyze fetal blood cells= hemolytic diseas of the fetus & newborn (erythroblastosis fetalis)
In rare case= anemia so severe that fetal hydrops occurs where edema & effusions into body cavities–> lead to death of fetus!
Severe Cases of Erythroblastosis & Fetal hydrops
by CDE Rhesus blood group sys & D or RH antigen is most dangerous
Maternal Y response occurs when fetus is D (Rh) + & mother is D (Rh) -
Placenta f
- exchnage gas, nutrition & electrolytes
- O2, CO2 & CO simple diffusion
- short term interruption of O2 supply is fatal
- transmission of maternal Y
* IgG transported from mother to fetus @ 14 wks. Fetus gains passive immunity - Hormone production by syncytiotrophoblast
- progesterone! By 4th month, placenta should produce enough to maintain preg & CL can degen
- also makes estrogen, hCG & lactogen/somatomammotropin
Synthetic esrogen diethylstilbestrol DES
cross placenta easily, can cause carcinoma of vagina & abnormalities of cervix & uterus in female
Also in male testes who were exposed to DES
Many viruses
rubella, cytomgalovirus, Coxsackie, variola, varicella, measels, poliomyelitis virus
Cross placenta w/o difficulty
Some can cause infections, which results in cell death & birth defects
Microorganisms
treponema, pallidum, syphilis & toxoplasma gondii
Damage brain & eyes
Most Drugs
cross w/o difficulty so serious damage
Heroin & cocaine can cause fetal habituation
Amniotic Fluid
Protective cushion
From 5th month fetus swallows it & fetal urine added dialy to amniotic fluid
polyhydramnios= excess >1500
oligo= decreased <400
