Fetal circulation Flashcards
Why is pulmonary blood flow minimal in fetuses?
There is no need for any significant pulmonary circulation since the placenta is the fetal organ of gas exchange
Where does blood flow to the placenta come from?
Umbilical arteries (branch of anterior iliac arteries)
Blood returns to the fetus from the placenta via what vessels?
Umbilical vein
What are the 3 fetal shunts?
Ductus arteriosis
Foramen ovale
Ductus venosus
What is the route of blood through the ductus arteriosis?
Superior vena cava–right atrium–right ventricle–pulmonic trunk–ductus arteriosus–aorta
What is the route of blood through the foramen ovale?
Inferior vena cava–right atrium–forament ovale–left atrium–left ventricle–aorta
What is the route of blood through the ductus venosus?
Umbilical vein–ductus arteriosus—inferior vena cava
Portal vein–ductus arteriosus–inferior vena cava
Ductus arteriosus and foramen ovale allow blood to bypass what?
Lungs
The ductus venosus allow umbilical and portal blood to bypass what?
Liver
Where is the greatest oxygen saturation in fetal blood?
Umbilical vein-80% (from placenta)
What are 3 circulatory readjustments at birth?
- Increased blood flow through lungs and liver
- Loss of blood flow through the placenta
- Closure of foramen ovale, ductus arteriosis, and ductus venosus
What occurs when there is increased blood flow though lungs and liver–a circulatory readjustment at birth?
Pulmonary and vascular resistance decreases
-Decreased RVP, pulmonary arterial BP
What occurs when there is a loss of blood flow through the placenta–a circulatory readjustment at birth?
Doubles the systemic vascular resistance
-Increased LAP, LVP, aortic BP
What occurs with the closure of foramen ovale?
Due to reversal of pressure gradient between RA and LA, flap closes
What occurs with the closure of ductus arteriosis?
Reversal of flow from aorta to pulmonary artery, and increased oxygen levels cause constriction of smooth muscle
