"Functional" closure of the ductus arteriosus within 18 to 24 hours after birth via smooth muscle constriction
After delivery, there is an _______ in arterial PO2, a drop in circulating ________ (produced in the placenta), and a drop in blood pressure within the lumen of the ductus (caused by the drop in ______). All these events promote constriction of the ductus arteriosus.