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