Now thrombin is also important because it actually goes back and creates many different positive feedback loops as we'll see in just a moment and that amplifies the effect. Now let's look at the intrinsic pathway because ultimately it's the intrinsic pathway that is affected by this medical condition we call Hemophilia A. So in the intrinsic pathway following the exposure of the surrounding tissue, following that cut in the blood vessel that basically stimulates the proteolytic activation of factor twelve. And then once factor twelve is activated it goes on to proteolytically activate factor eleven and that goes on to proteolytically activate factor nine. Now factor nine cannot by itself activate factor ten. What must happen is this protein that is not an enzyme.