Q. Concerning the mixture of arterial with venous blood what is the difference between the adult circulation and the human fetal circulation?
In the human fetal circulation there are two communications between venous and arterial blood characterizing an incomplete circulation one of them is the oval foramen, an opening between the right and the left atria of the fetal heart the other is the arterial duct, a short vessel connecting the pulmonary artery to the aorta, these communications close a few days after birth and so they are not present in the adult heart.