CVS Practice Test

The correct answer is the Foramen ovale, which plays a crucial role in fetal circulation by bypassing the lungs. In a developing fetus, the lungs are not functioning for gas exchange, as the fetus receives oxygenated blood from the placenta through the umbilical vein.

The inferior vena cava brings deoxygenated blood from the lower parts of the body to the right atrium, but rather than passing all of this blood into the right ventricle and thus to the lungs, a significant portion is shunted directly into the left atrium through the Foramen ovale. This allows oxygen-rich blood to flow into the left atrium, then into the left ventricle, and out into the body, ensuring that vital organs receive the oxygen they need.

In contrast, the ductus arteriosus is another fetal shunt that connects the pulmonary artery to the aorta, allowing some blood to bypass the lungs but through a different route. The ductus venosus directs blood from the umbilical vein to the inferior vena cava but does not specifically shunt blood from the inferior vena cava to the left atrium. The umbilical vein is responsible for bringing oxygenated blood from the placenta to the fetus, but it does