Then within hours, the darkness arteriosis constricts. And so eventually, the blood ceases to flow from the pulmonary trunk into the order. And finally, within days, as a result of that clamping process, the resistance inside the umbilical vein increases. That causes less blood to flow inside the umbilical vein and inside the doctor's venosis. And this eventually becomes non functional and ceases to function and ceases to exist. Now, another important change that takes place is the thickening of the left ventricle compared to the right ventricle.