1-fetal circulation

1. SMS 1053
Dr. Mohanad R. Alwan
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2. 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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3. The Placenta
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The circulatory system of the
mother is not directly connected
to that of the fetus, so the
placenta functions as the
respiratory center for the fetus
as well as a site of filtration for
plasma nutrients and wastes.
Water, glucose, amino acids,
vitamins, and inorganic salts
freely diffuse across the
placenta along with oxygen.
The uterine arteries carry
oxygenated blood to the
placenta, and permeates the
sponge like material there.

4. Anatomy and Physiology
Fetal 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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Facilitates gas and nutrient exchange between maternal
and fetal blood.The blood itself does not mix.

5. Fetal Circulation
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6. 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 Venosus and then into
the inferior vena cava
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7. 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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8. Fetal Circulation
Blood continues to travel from the inferior vena
cava to the ductus Venosus
Ductus Venosus: shunts a significant majority (80%) of
the blood flow of the umbilical vein directly to the inferior vena
cava.
Ductus Venosus it allows oxygenated blood from the placenta
to bypass the liver and puts blood into the hepatic veins.
Small amount of blood routed to growing liver
Increased blood flow leads to large liver in newborns
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9. What happens to the blood after it
reaches the right atrium??
Blood flows right into the left atrium through
the foramen ovale.
 Alamak,What is that? It’s Small opening in the
septum of the heart
Foramen ovale
Small opening in the septum of the heart
Completely by passes the non-functioning lungs
Here again it mixes with a smaller amount of
deoxygenated blood from the pulmonary
veins.
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10. F.C
Some of the blood entering the right atrium does not
pass directly to the left atrium through the foramen ovale,
but enters the right ventricle and is pumped into the
pulmonary artery.
 In the fetus, there is a special connection between the
pulmonary artery and the aorta, called the ductus
arteriosus, which directs most of this blood away from
the lungs (which aren't being used for respiration at this
point as the fetus is suspended in amniotic fluid)
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11. Ductus Arteriousus
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12. Fetal Circulation
After it proceeds to the left ventricle where it is
pumped to the heart and brain
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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14. 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 by passes 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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15. 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
Some of the blood moves from the aorta
through the internal iliac arteries to the umbilical
arteries, and re-enters the placenta, the
maternal circulation
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16. 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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17. 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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18. 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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19. 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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20. 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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21. 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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Overall anatomic changes are not complete for weeks

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