Blood clotting after an injury is very important to prevent excessive bleeding which can lead to shock or even death. clotting is a rather complex process and involves many proteins and molecules (factors) in the body. A blood clot also called thrombus is a response to a break in blood vessel and it’s made up of platelet aggregates and a mesh of a protein called fibrin. When tissues are damaged they expose a certain protein to blood cells and this in turn triggers a chain reaction that leads to formation of clots.
In certain cases blood clots form in a healthy uninjured blood vessel and this can cause blockage of blood flow to certain areas leading to certain problems. Examples are stroke which can be caused by blockage of blood flow to the brain due to clots in brain blood vessels and heart attack caused by blockage of blood flow to certain parts of the heart.