When there is not enough VWF in the blood, or when it does not work the way it should, the blood takes longer to clot. Blood is carried throughout the body within a network of blood vessels. When tissues are injured, damage to a blood vessel may result in leakage of blood through holes in the vessel wall. The vessels can break near the surface, as in a cut. Or they can break deep inside the body, making a bruise or an internal hemorrhage.
Platelets are small cells circulating in the blood.
There are 150 to 400 billion platelets in a normal litre of blood. The platelets play an important role in stopping bleeding and beginning the repair of injured blood vessels. When a blood vessel is damaged, there are four stages in the normal formation of a clot. The blood vessels constrict to slow the flow of blood to the injured area. This is called platelet adhesion.