1 Fetal Circulation
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Transcript of 1 Fetal Circulation
Fetal Circulation
Dr. Mohanad R. Alwan
SMS 1053
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Anatomy and Physiology
Fetus depends on placenta to meet O2 needs while organs continue formation
Oxygenated blood flows from the placenta To the fetus via the umbilical vein After reaching fetus the blood flows
through the inferior vena cava
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The Placenta
Facilitates gas and nutrient exchange between maternal and fetal blood.
The blood itself does not mix.
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Anatomy and PhysiologyFetal Circulation
Umbilical cord 2 umbilical arteries: return non-oxygenated blood,
fecal waste, CO2 to placenta 1umbilical vein: brings oxygenated blood and
nutrients to the fetus
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Fetal Circulation
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How does the blood move??
Umbilical VEIN carries oxygenated blood and nutrients from the placenta to the fetus
Where does the vein enter?? At the navel and ascends into the liver
How is the blood dispersed?? ½ of the blood enters the liver while the other half
comes into the ductus venous and then into the inferior vena cava
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Foramen Ovale
Blood is shunted from right atrium to left atrium, skipping the lungs.
More than one-third of blood takes this route.
Is a valve with two flaps that prevent back-flow.
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Ductus Arteriousus
The blood pumped from the right ventricle enters the pulmonary trunk.
Most of this blood is shunted into the aortic arch through the ductus arteriousus.
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Fetal Circulation
Blood continues to travel from the inferior vena cava to the ductus venosis
Ductus Venosis Small amount of blood routed to growing liver Increased blood flow leads to large liver in
newborns
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What happens to the blood after it reaches the right atrium??
Blood flows right into the left atrium through the foramen ovale. What is that?
Small opening in the septum of the heart
Here again it mixes with a smaller amount of deoxygenated blood from the pulmonary veins.
After it proceeds to the left ventricle where it is pumped to the heart and brain
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Fetal Circulation
Foramen ovale Small opening in the septum of the heart Completely bypasses the non-functioning lungs
Blood continues journey to the left ventricle blood is then pumped into the aorta
Blood is circulated to the upper extremities Blood then returns to the right atrium
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What about the rest of the blood??
The blood still in the right atrium goes into the right ventricle then to the pulmonary artery.
Once there most of the blood bypasses the lungs and heads to the aorta through the ductus arteriosus.
About 15% of the blood flows through lungs to the right atrium by way of the pulmonary veins
Pulmonary arteries Small amount goes to the maturing lungs
Rest of blood is shunted away from lungs by ductous ateriosus back to aorta
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What is happening further down??
Common iliac arteries branch into the external and internal iliacs.
The blood in the internal iliacs come into the umbilical arteries and flow back to the placenta to gather oxygen and to get rid of the waste products
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Fetal Circulation
Low pressure system Lungs are closed Most oxygenated blood flows between the atria of
the heart through the foramen ovale This oxygen rich blood flows to the brain through
the ductus arteriosus
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What happens after birth?
once the baby is born and the lung, renal, digestive and liver functions are working the fetal circulation undergoes some changes since they are no longer needed
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Conversion of Fetal to Infant Circulation
At birth Clamping the cord shuts down low-pressure
system Increased atmospheric pressure(increased
systemic vascular resistance) causes lungs to inflate with oxygen
Lungs now become a low-pressure system Pressure from increased blood flow
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Conversion: Fetal to Infant Circulation
In the left side of the heart causes the foramen ovale to close
More heavily oxygenated blood passing by the ductus arteriosus causes it constrict
Functional closure of the foramen ovale and ductus arteriosus occurs soon after birth
Overall anatomic changes are not complete for weeks
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Conversion (cont)
What happens to these special structures after birth? Umbilical arteries atrophy Umbilical vein becomes part of the fibrous support
ligament for the liver The foramen ovale, ductus arteriosus, ductus
venosus atrophy and become fibrous ligaments
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Overview of Conversion
Umbilical cord is clamped Loose placenta Closure of ductus venosus Blood is transported to liver and portal
system
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Fetal vs. Infant Circulation
Fetal Low pressure system Right to left shunting Lungs non-functional Increased pulmonary
resistance Decreased systemic
resistance
Infant High pressure system Left to right blood flow Lungs functional Decreased pulmonary
resistance Increased systemic
resistance
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