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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
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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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Three shunts are present in fetal life:
1. Ductus venosus: connects the umbilical
vein to the inferior vena cava
2. Ductus arteriosus: connects the main
pulmonary artery to the aorta
3. Foramen ovale: anatomic opening between
the right and left atrium.
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How does the blood move??
• Umbilical VEIN carries oxygenated blood
and nutrients from the placenta to the
fetus
• Blood continues to travel from the inferior
vena cava to the ductus Venosus
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Fetal Circulation
• 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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What happens to the blood after it
reaches the right atrium??
• Blood flows right into the left atrium
through the foramen ovale.
• Here again it mixes with a smaller amount
of deoxygenated blood from the
pulmonary veins.
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Fetal Circulation
• 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
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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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Placenta
Umbilical Vein
Umbilical Arteries
Liver
Ductus Venosus
Inferior Venacava
Right Atrium
Foramen Ovale
Right Lung
Arch of Aoarta
Ductus Arteriosus
Left Atrium
Left Ventricle
Right Ventricle
Portal Vein
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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 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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What is happening further down??
• 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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PATHWAY
Oxygenated blood from the placenta
through umbilical vein
fetus
liver
Receives deoxygenated blood from the portal vein
through ductus venosus
Inferior vena cava
Right atrium of heart
through foramen ovale
Left atrium of the heart
Left ventricle of the heart
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During ventricular systole
Left ventricular blood Right ventricular blood
pumped with < o2
content
Ascending aorta and distributed is discharged
by their branches to the heart, Pulmonary arteries
head,neck,brain,arms. Ductus
arteriosus
Descending aorta
Hypogastric arteries
Umbilical arteries
Placenta
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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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• at birth
• Closure of the Ductus Venosus.
• Closure of the Foramen Ovale.
• Closure of the Ductus Arteriosus.
