Before a baby is born, what is one key structure of fetal circulation?

The foramen ovale is a crucial structure of fetal circulation, playing a vital role in how blood is routed in a developing fetus. During gestation, the fetus is not using its lungs for oxygen exchange; instead, it relies on the placenta for oxygenated blood. The foramen ovale is a small opening between the right and left atria of the heart, allowing blood to bypass the nonfunctioning lungs and flow directly from the right atrium to the left atrium.

This adaptation helps ensure that the oxygen-rich blood from the placenta can be efficiently delivered to the body's systemic circulation while minimizing the amount of blood that needs to be sent to the pulmonary circuit, which is largely bypassed during this stage. After birth, with the onset of breathing, the pressure dynamics in the heart change, causing the foramen ovale to close and become a functionally insignificant part of the anatomy.

Other structures mentioned, like the ductus arteriosus and umbilical vein, also play significant roles in fetal circulation. The ductus arteriosus allows the blood to flow from the pulmonary artery to the aorta, bypassing the lungs, while the umbilical vein carries oxygenated blood from the placenta to the fetus. However, the