Maternal/Fetal Circulation Flashcards
What structures form the placenta?
1) Placental villus
2) fetal vessels
3) chorionic tissue (outermost extraembryonic membranes)
What happens to maternal blood volume during pregnancy?
↑ ~ 45% w/ single
↑ ~ 100% w/ multiples
During which trimester does maternal blood volume ↑ the most?
second
What is the erythropoietic effect?
↑ in maternal erythrocyte volume
~ 33%
What happens to the maternal hematocrit?
↓
What happens to maternal plasma volume during pregnancy?
Why?
↑ ~ 50%
↑ progesterone/estrogen cause vasodilation ->
↓ renal perfusion pressure ->
activates renin-angiotensin and AVP release ->
↑ plasma vol
What happens to maternal CO during pregnancy?
↑ ~ 45%
primarily the result of ↑ SV
What happens to maternal TPR during pregnancy?
↓ due to ↑ progesterone/estrogen
What happens to maternal MAP during pregnancy?
↓ at midpoint
↑ at end term
Maternal CO during pregnancy directed to what specific tissues?
large ↑ renal blood flow
large ↑ uterine blood flow
↑ heart, skin, breast blood flow
no ∆ to brain, gut, skeleton
4 AV shunts in fetal circulation?
1) placenta
2) ductus venosus
3) foramen ovale
4) ductus arteriosis
Action of placenta as fetal AV shunt?
shunts blood L to R from:
fetus’ lower body to umbilical vein to inf vena cava
Action of ductus venosus as fetal AV shunt?
shunts blood from:
liver directly from umbilical vein (oxygenated) to IVC
Action of foramen ovale as fetal AV shunt?
directly shunts from R to L atria
Action of ductus arteriosis as fetal AV shunt?
shunts blood R to L from:
pulmonary artery to aorta
downstream of supply to head/up body
Fetus vs neonate:
R and L sides of heart
fetal: pump in parallel
neonate: pump in series
Fetus vs neonate:
CO
fetal: CO is combined output of L and R side of heart. R output = 66%, L output = 34%
neonate: CO is output of L heart. R and L outputs are equal.
∆ from fetal flow to neonate flow is initiated and completed when?
newborn takes first breath
Oxygen saturation of blood leaving fetal heart vs entering heart?
blood leaving has less O2 than blood entering
Oxygen saturation of fetal blood in R vent vs L vent?
R has less O2 (gets deoxy from brain and up body).
L only gets deoxy from lungs.
Oxygen levels in fetus vs mother?
Why?
fetus O2 is much lower
fetal Hb has higher affinity for O2
Benefit of low O2 levels in fetus?
stimulates cell growth and differentiation
During birth, are umbilical arteries or umbilical vein constricted?
arteries
reduces circulating O2
During birth, auto-transfusion of maternal blood to fetus through the placenta accounts for how much of the baby’s total blood volume?
~ 1/3
Breathing is initiated by what?
Mediated by?
hypoxia and hypercapnia (high CO2)
chemoreceptors
tactile stim
cold
1st breath req’s what amount of H2O?
To move what amount of air?
60 cm H2O
40 ml air
2nd breath req’s what amount of H2O?
40 cm H2O
1st breath does what in the lungs?
opens alveoli
creates air-H2O interface
1st breath affects plumonary vasculature how?
large ↓ in pulmonary resistance ->
↑ flow thru pulmonary vessels
Blood flow away from pulmonary artery into lung vessels results in what?
↓ pulmonary artery P
↓ R vent P
About when do newborn lungs reach adult compliance?
How much H2O is req’d for respiration then?
~ 1 hr
2.5 cm
↓ pulmonary artery P causes what change in flow?
direction of ductus arteriosis flow reverses (now L to R, aorta to pulm artery)
Ductus arteriosis flow stops when?
Permanently closes when?
1 wk
1 mo
What happens to atrial pressure after birth?
L atrial P > R atrial P
What does change in atrial pressures cause?
closure of foramen ovale ->
circulation now serial instead of parallel
What happens to ductus venosus after birth?
closes ~ 3hrs post ->
↑ P in portal vein ->
establishes portal circulation in liver
Breakdown of fetal heart inflow by system/percentage?
lower body 69%
up body 21%
coronary circulation 3%
lungs 7%
