1.19 Fetal Circulation

The fetus has respiratory functions as welll as input of nutrients and waste elimination carried out where from the body? (within or outside)

Outside of the body.

Fetal circulation can occur because of what three things?

• The placenta

• The presence of shunt pathways (foramen ovale and patent ductus arteriosus)

• Low levels of pulmonary blood flow

The right heart pressure in a fetus is what in comparison to the left heart?

Really high versus the left heart.

What two communications close in a fetus after birth?

The foramen ovale (PFO) and the patent ductus arteriosus (PDA).

How is fetal blood ocygenated?

Via the placenta.

The umbilical vein holds oxygenated or deoxygenated blood?

Oxygenated blood.

The umbilical arteries holds oxygenated or deoxygenated blood?

Deoxygenated blood.

The major part of the blood that has been oxygenated by the placenta and returns via the umbilical vein, then leads oxygenated blood where?

To the IVC via the ductus venosus.

Where does the IVC take oxygenated blood to next in the fetus?

To the RA.

In a fetus, once oxygenated blood enters the RA, what happens next and where does it go?

Majority of the blood is shunted to the left, going from RA to LA via the eustachian valve, which will then go into the LV, Ao, and the systemic system. Some of it might trickle into the RV from the RA, which would go to the pulmonary artery. There is a connection between the pulmonary artery and the Ao called the ductus arteriosus, which redirects blood from the pulmonary artery to the Ao. A small amount of blood continues into the pulmonary artery to supply the lungs for growth, NOT oxygenation.

In normal conditions, the PDA and the PFO will do what shortly after birth? What happens to the right heart pressures?

Close. Right heart pressures will also decrease to normal levels.