Physiology of Fetus and Placenta Flashcards Preview

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Flashcards in Physiology of Fetus and Placenta Deck (21)
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How many cell layers are between maternal and fetal blood?

Just 2.


How does fetus adapt to living at a lower PO2?

Fetal hemoglobin, shunts most oxygenated toward toward brain.


What's different about fetal hemoglobin?

It has a higher affinity for oxygen.


3 important aspects of fetal vasculature (he calls them shunts)?

Ductus venosis - brings highly oxygenated umbilical vein blood to IVC.
Foramen ovale.
Ductus arteriosis.


Review: What does the foramen ovale do? When does it close?

Shunts oxygenated blood from R. atrium to L. atrium, bypassing the lungs.
Closes when L. ventrical becomes dominant.


Review: What does the ductus arteriosis do? When does it close?

Shunt from pulmonary a. to descending aorta, bypassing lungs.
Closes with baby's first breath.


How does the trophoblast prevent immune rejection despite paternal HLA antigens? How does this work?

Expression of HLA-G.
HLA-G doesn't present antigens, but prevents killing by NK cells.


Which cells produce hormones? What do they make? (4 things)

Polarized epithelium (hormones go straight to maternal blood) of the syncytiotrophoblast.
Makes hCG, hCS (don't worry about it), estriol, and progesterone.


How many days after ovulation can hCG be detected in maternal serum if pregnancy occurred?

Detectable in serum 8 days later.


hCG activity?

Maintain corpus luteum, binds TSH receptors.


How is monitoring hCG levels useful?

Abnormal levels for gestational age can indicate problem with pregnancy.


4 molecules unique to fetus that can be measured in maternal serum?
Utility of measuring them?

Alpha-fetoprotein, unconjugated estriol, hCG, inhibin A.
Abnormal levels can be indicative of chromosomal abnormalities.


What's special about fetal adrenal steroid production?

The fetal adrenal glands must work with the placenta, because each has a necessary enzyme that the other lacks.
Placenta can make progesterone, but not E2 from it.
Fetal adrenal can make E2 from progesterone, but can't make progesterone from cholesterol.


What enzyme do the fetal adrenals lack? What does it do?

Lacks 3beta-HSD.
Converts DHEA to T and estrogens,
pregnenolone to cortisol.
(probably not a high yield fact)


What enzyme for steroid production does the placenta lack?

Lacks P450c17 for conversion of pregnenolone to DHEA.
(probably not a high yield fact)


Effect of progesterone on immune system?

Inhibits production of cytolytic cytokines that might cause trophoblast rejection.


What's the main starting material that the placenta used to make estrogens?

DHEA-sulfate (DHEAS) from fetal adrenals.


Which estrogen is derived almost exclusively from fetal adrenals?

(thus can be used to monitor fetal health)


Which part of the fetal cortex is biggest?

Inner fetal zone, which makes DHEAS.
(and not much cortisol)


Is giving cortisol to pregnant women harmful to the fetus? What if you need to give cortisol to the fetus?

Not really. Fetus has enzyme that rapidly breaks it down.
(probably only up to a point.. there are all those studies on how in-utero cortisol exposure affects later outcomes)
If giving cortisol to fetus, must give synthetic kind that won't be broken down.


Broad effects of estrogens produced by placenta?

Change maternal physiology.
Increase uterine blood supply.
Promote partuition (via CRH, myometrial gap junctions).
Promote breast maturation for lactation.