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24 Cards in this Set

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How does flow through the heart differ between an adult and a fetus?
1. Foramen ovale right atrium to left atrium 2. Increased pulmonary artery resistance shunts most blood through Ductus arteriosus from the pulmonary artery into the aorta
Trace an RBC from oxygenation at the placenta and back (about five steps)
1. Umbilical vein flows through liver 2. Shunted from liver to ductus venous to Vena Cava 3. Right atrium to left atrium via foramen ovale 4. Left ventricle to aorta 5. abdominal aorta branches to umbilical arteries to placenta
List the three shunts in fetal circulation.
Ductus venosus (portal vein shunt to vena cava, avoids sinusoids), foramen ovale (rt atrium to left atrium), and ductus arteriosus (pulmonary artery to aorta, avoiding the lungs)
Where do the two umibilical arteries originate from?
Iliac arteries
What causes the increase in pulmonary vascular resistance found during fetal life?
The elasiticity of the uninflated lung
True/False: Oxygen saturation in the fetus is generally about the same as in the adult human.
False, normally the highest is about 80-85%
True/False: the decreased saturation affects the ability of the fetal blood to transport nearly as much oxygen as the mother's blood.
False, it normally is able to transport as much
In the fetus which develops the higher pressure: the right atrium or the left atrium?
The right atrium (which promotes blood flow from right to left across the oframen ovale and through the ductus arteriosus)
List three fetal response to stress circuation (ie decreased oxygen delivery).
1. Changes in oxygen extraction and consumption 2. Redistribution of Placental venous return 3. Redistribution of Cardiac output
What causes an increase in oxygen extraction in response to fetal hypoxia?
Increase in umbilical venous resistance (probably improves maternofetal gas exhange)
True/False: Oxygen consumption in the fetus is capable of ecreasing by up to 1/3 in response to stress without producing acidosis
TRUE
What is the primary target of blood pumped from the left ventricle?
The head and forelimbs
Describe the fetal hypoxic stress response in redistribution of placental venous return.
More blood is shunted (up to 80% more) through the foramen ovale resulting in greater blood ending up in the head.
What is the proposed mechanism for redistribution of placental venous return?
Ductus venosus dilation or hepatic constriction resulting in an increase in umbilical venous return to the inferior vena cava
When the lungs inflate open first breath what happens to pulmonary vascular resistance?
It falls dramatically
Resistance gradual increases/decreases over the last trimester
decreases
List three factors which influence the closure of the ductus arteriosus when the pressure differential reverses upon first breath and flow now goes from aorta to pulmonary veins.
1. Increase in pOxygen 2. Decrease in pCarbon dioxide 3. Increase in pH
What causes closure (or probe patency) of the foramen ovale after birth(include ductus venosus in your answer)?
Decrease in venous return from placenta (ductus venosus closes) resulting in a decreased rt ventricle output, Also the lung inflating decreases pulmonary vascular resistance causing the one way valve to close
What two shunts close or almost close upon lung expansion?
Ductus arteriosus and foramen ovale
Severe pulmonary valve stenosis/atresia and hypoplastic right ventricle are both examples of what type of an obstruction?
Right Heart obstruction
What is the effect of a so-callend right heart obstruction?
With little lung blood flow (only the amount able to cross the small pulmonary valve) the newborn will become profoundly hypoxemic
How does the fetus compoensate for hypoplastic left heart syndrome?
The ductus arteriosus swells and the right ventricle/atria hypertrophies
If left untreated what is the prognosis for the left hypoplastic heart syndrome?
Acidosis and death
Over the long term what is the effect of fetal arrythmias?
Congestive heart failure and resulting development of fetal hydrops.