FETAL CIRCULATION S-2-CVSM72
LEARNING OBJECTIVES
At the end the lecture the student should know the following:
Problems with persistence of fetal circulation after birth
FETAL CIRCULATION
functioning.
low to placenta.
UMBILICAL VESSELS
Located at the navel and enters the liver
THE PLACENTA
SHUNTS OF THE FETAL HEART
Foramen ovale
Connection between the right and left atria
Ductusarteriosus
Connection between the truncuspulmonalis and the aorta
FORAMEN OVALE
-flow.
left atrium, skipping the lungs.
-third of blood takes this route.
DUCTUS ARTERIOSUS
ary trunk.
ductusarteriosus.
UMBILICAL VEIN TO PORTAL CIRCULATION
irculation allowing
the liver to process nutrients.
jority of the blood enters the ductusvenosus, a shunt which bypasses
the liver and puts blood into the hepatic veins.
FETAL CIRCULATION
ients from the placenta
to the fetus
e liver, other half into the ductus venous and then
into the inferior vena cava
IN THE RIGHT ATRIUM
m the superior vena cava.
pulmonary veins.
e heart and
brain
REMAINING BLOOD IN RIGHT ATRIUM
pulmonary artery.
ductusarteriosus.
t 15% of the blood flows through lungs to the right atrium by way of
the pulmonary veins
INTERNAL ILIAC ARTERIES
nch into the external and internal iliacs.
back to the placenta to gather oxygen and to get rid of the waste products.
FINALLY THE BIRTH!!!
o thermal., tactile and visual
o Results in a decrease in fetal blood PO2, increase in PCO2 and pH to
decrease
AT BIRTH
from fetal to postnatal circulation happens very quickly.
AFTER BIRTH?
and liver functions are
working the fetal circulation undergoes some changes since they are no longer
needed
FETAL LUNG FLUID
functional residual capacity (FRC)
1/3rd of the fluid is squeezed out of the lungs as the baby passes through the
birth canal
FIRST BREATH
be generated to overcome the
viscous fluid found in the lungs. This pressure is -40cmH20. Up to 100cmH20!
exhaled. The remaining amounts help to create the residual volume
s .005L/cmH20 and the airway resistance is
30cmH20/L/sec
CHANGES IN CIRCULATION
ce
falls.
xic vasoconstriction
caliber of the extra alveolar vessels
AS THE PVR DECREASES…..
blood flows through the lungs which allows for more blood to come to
the left atrium. The results in a increase pressure in the left atrium which
allows the flap of the foramen ovale to close. The closure is also helped by
the fall in pressure in the right atrium as the umbilical flow stops.
ue to the increase
in PO2.
EFFECTS OF INCREASED PO2
-50mmHg to allow the
ductusarteriosus to close. If it is not reached the ductus will not close and the
PVR will remain elevated causing Persistent Pulmonary Hypertension of the
Newborn (PPHN)
-48
hours after birth the ductus will re open
VITAL SIGNS OF THE NEWBORN
-50/min
130-150/min
-70/45
PERSISTENCE OF FETAL CIRCULATION:
nt foramen ovale each
characterize about 8% of congenital heart defects.
-rich and oxygen-poor blood; blood reaching
tissues not fully oxygenated. Can cause cyanosis.
around age two.
TREATMENT
methacin (prostaglandin synthetase inhibitor)