I am certain that placing pressure on a cut will constrict blood vessels manually, and encourages vascular spasms.
Vascular spasms are sudden, brief tightening of the muscle cells inside the walls of a blood vessels. It is the first response as the blood vessels constrict to allow less blood to be lost. In the second step, platelet plug formation, platelet stick together to form a temporary seal to cover the break in the vessel wall, the third step is the coagulation or blood clotting.
