Fetal Circulation

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Terms in this set (...)

Placenta
Exchange of gases , nutrients and wastes
Umbilical arteries
Carry de-oxygenated blood from the fetus to the placenta
Umbilical Veins
Carry oxygenated blood and nutrients to the fetus
PaO2 in umbilical arteries
20 mmHg
PaCO2 in umbilical arteries
55 mmHg
Fetal PaO2
30 mmHg
Fetal PaCO2
40 mmHg
Possible reasons for PaO2/ PaCO2 difference
•Shunting in placenta
•Metabolism in the placenta
•Regional variations in gas exchange areas of placenta
Umbilical cord
•2 arteries
•1 vein
•Surrounded by Wharton's jelly
Pressures in fetal vasculature
•Systemic = Low resistance
•Placental = Low resistance
•Pulmonary = High resistance
Normal shunts in fetus
•Foreman ovale
•Ductus arteriosus
•Ductus venosus
Foreman ovale & ductus arteriosus
Bypass lung
Ductus venosus
Bypasses liver
Fetal hemoglobin
Causes Left shift of Oxy-Hgb curve
Ductus arteriosus constricts due to ___
increased PaO2
Foremen ovale closes due to ___
pressure gradient changes
Trans-Pulmonary pressures must exceed ___ to allow air to enter the lungs
40 cwp
PaO2 increases causing ___
pulmonary vessels to dilate