Fetal circulation I
The relatively less-well-oxygenated blood entering the right atrium from the superior vena cava preferentially flows across the tricuspid valve into the right ventricle. From there it is ejected into the pulmonary trunk. Only a small portion flows to the lungs via the pulmonary arteries; the bulk goes into the descending aorta via the ductus arteriosus. Blood flow in the descending aorta supplies the abdominal organs and lower extremities and returns blood to the placenta via the umbilical arteries, thus completing the circuit.
1 minute clinical correlation