And so within hours, the ductus arteriosis will essentially constrict to a point where very little blood will actually flow between the pulmonary trunk and our eight order. So, once again, following the expansion of lungs, they release a protein called bradyclin. As oxygenated blood travels through the ductus arteriosis, that protein mixes with the oxygen, with the high oxygen content, and it causes the constriction of the ductus arteriosis. So as the pressure in the lungs falls below the systemic pressure, below the pressure inside our order, less blood flows via this constricted ductus arteriosis, and it eventually ceases to exist. So we see that within minutes, the Forayman Or valley closes. As a result, of the reversal and pressure between the right atrium and the left atrium.