Now let's move on to the st segment. What exactly takes place within our st segment? So within the st segment, that contraction increases that hydrostatic pressure. And what that causes is these two semi lunar valves, our pulmonary semi lunar valve and our aortic semilunar valve, to basically open up. And as those valves open up, all that blood flows from the ventricles into our arteries. So the left ventricle sends that oxygenated blood into the order, while the right ventricle sends our deoxynated blood into the pulmonary arteries and eventually into our lungs.