Fetal Circulation Flashcards
What does maternal blood supply the placenta with?
Oxygen, gas exchange, proteins, enzymes, sugars, plasma
What makes fetal Hgb different from maternal Hgb?
Fetal Hgb can bind with and carry up to 20% - 30% more O2 than maternal Hgb.
Why does placental blood have as much as 50% more O2 concentration than maternal blood?
Because fetal Hgb has a higher affinity to O2 than maternal Hgb. It can bind to and carry more O2 than maternal Hgb.
What is the role of the placenta?
Gas exchange; delivery of all nutrients, proteins, sugars; embryonic waste removal
What is the role of the umbilical vein?
To carry oxygen rich blood from the placenta to the fetus.
How does the umbilical vein enter the fetus?
It passes through the umbilical ring/umbilicus and travels along the abdominal wall anteriorly.
As the blood nears the liver, where does it go?
About 1/2 enters the liver, while the other 1/2 is shunted through the ductus venosus to the IVC.
Where are fetal RBC’s produced?
At first they are produced in the yolk sac. At around 11-14 weeks they are produced in the liver.
What happens when the blood reaches the IVC?
The O2 rich blood from the umbilical vein mixes with the low O2 blood from the lower extremities in the IVC.
Where does blood flow from the IVC go?
Blood from the IVC enters the RA where most is shunted to the LA via the foramen ovale.
Does all of the blood in the RA shunt to the LA?
No, some blood goes to the RV, then to the PA and on to the lungs for tissue perfusion and cell growth.
Does all of the blood in the PA go to the lungs?
No, most of the blood is shunted to the AO via the ductus arteriosus.
What is the purpose of the ductus arteriosus?
It helps to lower blood pressure before going to the brain.
Where does blood from the SVC go?
This is returning low O2 blood from the upper extremities. It returns to the RA, where some will go to the RV and some will be shunted to the LA and on…
Where does the blood in the descending AO go?
This is partially oxygenated blood and will perfuse the lower regions and lower extremities.
Once the blood has perfused the lower regions and lower extremities, where does it go?
The lower O2 blood will return to the placenta for gas exchange via the 2 umbilical arteries.
After the baby is born and the lungs inflate, what happens within the lungs?
Resistance in the lungs decreases.
As a result of the post-natal decrease in resistance within the lungs, what happens within the right heart?
The decreased resistance within the lungs leads to an increased venous return to the right heart.
How does the post-natal decrease in right heart pressures effect the left heart?
With the decrease in right heart pressures there is an increase in left heart pressures.
When do the foramen ovale, ductus venosus, and ductus arteriosus close?
They should close within 48-72 hours after birth.
What does the foramen ovale become post-natally?
The fossa ovalis
What does the ductus arteriosus become post-natally?
The ligamentum arteriosum
What does the ductus venosus become post-natally?
The ligamentum venosum
What do the umbilical arteries become post-natally?
The umbilical ligament and the superior vesial artery.
What does the umbilical vein become post-natally?
The ligamentum teres
How long does it take for fetal hemoglobin to change post-natally?
Up to 6 months
What is the pressure like within the fetal heart?
Prior to birth, pressure is higher within the right heart and lower within the left heart.
