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Old 10-10-2013
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Question Fetal Circulation


I'm a bit confused with the circulation.

Just to clarify I THINK this is how it goes according to FA / Kaplan

1) Umbilical Vein -> Ductus Venosus -> IVC -> Foramen Ovale -> Left Atria -> Left Ventricle ->Aorta. (FA Version)

2) It was mentioned in Kaplan 2010 Umbilical Vein -> Right Atrium -> Right Ventricle -> Pulmonary Artery -> Ductus Arteriosus -> Aorta -> Systemic Circulation.

I watch that segment atleast 10 times to see if I missed anything and he briefly mentions about the foramen ovale circulation.

So I am assuming that both mixes oxygenated blood and deoxygenated blood. (If I add the Kaplan Notes and First Aid 2013 together)

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Old 10-10-2013
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Both are correct!

Once blood in the right atrium, it has two options; either go through foramen ovale or go through the tricuspid valve down to the right ventricle.

Google Fetal Circulation images to understand further.

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Old 10-10-2013
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Blood reaches right atrium 2ways:
1. Oxygenated blood via IVC (67% oxygenated)
2. Deoxygenated blood via SVC (40% ox)
After that it can go either way, left atria or rt ventricle. But from IVC it mostly goes directly to left atrium through foramen ovale. That's why blood that goes thru the Lt atria->Lt ventricle->aortic arch branches, is abt 65% oxygenated.
From SVC majority goes rt atria-> rt ventricle -> pulmonary artery-> ductus arteriosus-> descending aorta, descending aorta lastly carries 60% oxygenated blood ( Ductus arteriosus opens after aortic arch branches).
So, there is mixing of blood all through the pathway. But roughly majority goes like above.
Hope this helps..
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Anatomy-, Cardiovascular-, Embryology-

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