Oxygenated blood from the placenta in the umbilical vein shunts at the level of the liver through the ductus venosus and from there flows into the inferior vena cava (IVC). The IVC and the superior vena cava (SVC) both drain into the right atrium (RA). From the right atrium, the oxygenated blood goes via the tricuspid valve to the right ventricle, and from there it enters the pulmonary artery. A small portion goes to the lungs, not for exchange but to supply oxygen and blood to the lungs.
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