Download Fetal Circulation

Fetal Circulation
Objectives
Discuss anatomy and physiology of fetal
circulation
Compare and contrast fetal circulation
to infant circulation
Define specialized structures of fetal
circulation
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
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
A/P 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
A/P Fetal Circulation
Blood continues to travel up the inferior
vena cava
Empties into the right atrium of the
heart
The blood then passes to the left
atrium through the foramen ovale
A/P 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
A/P Fetal Circulation
From the right atrium, the blood goes
to the right ventricle then to the
pulmonary arteries
Pulmonary arteries
Small amount goes to the maturing lungs
Rest of blood is shunted away from
lungs by ductous ateriosus back to
aorta
A/P Fetal Circulation
Blood travels back from aorta to the
two umbilical arteries to the
placenta
The placenta will re-supply the blood
with oxygen
Fetal circulation is a low-pressure
system
A/P 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
Conversion of Fetal to Infant
Circulation
At birth
Clamping the cord shuts down lowpressure 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
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
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
Overview of Conversion
Umbilical cord is clamped
Loose placenta
Closure of ductus venosus
Blood is transported to liver and portal
system
Loss of placenta also leads to
Overview of Conversion
First breath
Lungs expand and fluid is expelled
Decreased pulmonary resistance
Increased pressure in left atrium
Closure of foramen ovale
Overview of Conversion
Loss of placenta
Increased systemic resistance
Pressure in right atrium decreased
Change from right to left shunting to
left to right blood flow
Increased O2 levels in pulmonary
circulation
Closure of the ductus arteriosus
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
Summary
Reviewed anatomy and physiology of
fetal circulation
Discussed conversion from fetal to
infant circulation
Compared fetal to infant circulation
Determined outcome of special features
associated with fetal circulation after
birth