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19 Cards in this Set

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describe formation of zygote, morula, embryo, and trophoblast
HY Embryo: p. 12
1.egg becomes fertilized in fallop tube==>zygote
2. enters uterine cavity as solid mass of cells (morula)
3. fluid accumulates within cell mass:
-inner cell mass: embryo
-outer cell mass: trophoblast
4. b/w inner cell mass (embryo) and trophoblast, the amniotic cavity forms
5. outer cell mass (trophoblast) invades the endometrium
types of trophoblasts in placenta parenchyma:
CYTOTROPHOBLAST gives rise to:
-intermediate trophoblast (invades uterus & vessels)
-syncytiotrophoblast (lines placental villi and provides transfer from maternal to fetal compartment)
what blood does the syncytiotrophoblast have contact with?
The syncytiotrophoblast is bathed by maternal blood. it is separated from fetal blood by endothelial cells.
fetal membranes
*genetically identical to fetus
*avascular, no nerve cells

2 layers:
1. amnion (inner)- surrounds amniotic cavity
2. chorion (outer)-attaches to decidua (bv, etc.)

*The amnion and chorion fuse at 13-14 wks
-when do fetal membranes (chorion/amnion) rupture?
-What causes this?
-fetal membranes (chorion/amnion) rupture near delivery.

-Caused by:
*MMP's (Matrix Metalloproteinases--break down proteins in ECM)

*TNF-alpha (increase collagenase activity & activate inflammatory pathways)
*IL1 (ditto)
*PGE2, PGF2 (ditto)
placental fxn
-maintains preg and fetus
-1st trimester: produce hormones
-2nd-3rd trimesters: nutrient transfer b/w mother and fetus:
1.Transit across placental membranes
a.passive diff, facil diff transport
(glucose, certain aa, Ca2+)
c.endocytosis, exocytosis
(IgG, LDL)

2. Eliminate waste products
-fetal liver immature
-eliminates bile acids

3.Respiratory fxn
-rapid diff
-HbF has higher aff for O2 and lower aff for CO2
risk factors for placenta previa
-previous placenta previa
-multiple gestation
vasa previa
"previa"=cover cervical os

-fetal vessels ("vasa"=vessels) traverse the membranes in lower uterine segment and cover the cervical os ("previa"=cover cervical os)
placenta abruption
premature separation of the normally implanted placenta
-often caused by adherent retro placental clot
risk of placenta abruption
-mult gestations
-maternal trauma
-maternal smoking
what is functional unit of placenta
chorionic villi
where are placenta and fetal membranes derived from?
fetal tissues

(fetal membranes=amnion & chorion)
is there direct mixing of maternal and fetal blood
complications of abnl placental implantation (previa, accreta) or early placental separation?
significant maternal hemorrhage
what can cause significant maternal hemorrhage?
complications of abnl placental implantation (previa, accreta) or early placental separation
monozygotic pregnancy, timing of cleavage of fertilized ovum
better to cleave the fertilized ovum SOONER:
-days 2-3: 2 chorion, 2 amnion
-days 3-8: 1 chorion, 2 amnion
-days 8-13: 1 chorion,1 amnion
-days 13-15:conjoined twins
what is the greatest perinatal mortality risk?
monoamniotic twins (1 amnion): perinatal mortality risk is >20%
what is risk for monochorionic, diamniotic twins?
-risk d/t "sharing" a placenta:
==>unequal distrib of blood b/w twins
Placenta previa
=implantation of placenta over cervical os
1.Total placenta previa: placenta completely covers cervical os
2.Partial placenta previa:
partial occlusion of cervical os
3. Marginal placenta previa:
placenta encroaches on margin of cervical os

*Placenta forms abnl attachment to uterine wall
*Absence of decidua basalis (=maternal portion of placenta; =uterine lining (endometrium) during preg)
*Types (from better to worse, more common to less common)
1."A"ttached directly to myometrium ("A"ccreta)
2."IN"vade myometrium ("IN"creta)
3."PE"netrate myometrium ("PE"rcreta)