Question: what is the function of a patent opening between the left and right atria in a fetus?
Answer: The hole between the top two heart chambers (right and left atrium) is called a patent foramen ovale (PFO). This hole allows the oxygen rich blood to go from the right atrium to left atrium and then to the left ventricle and out the aorta. As a result the blood with the most oxygen gets to the brain.