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A normal blood clotting process begins when the body sustains an injury to any blood vessels. The clotting process stops blood loss, creates a protective barrier, repairs the damage tissue and finally dissolves the protective barrier. The entire clotting process is known as hemostasis.
During a normal clotting process, after a cut or other injury, an event called vasospasm can trigger the smooth muscles in small blood vessels to constrict. Vasospasm might reduce blood loss almost instantaneously. In another step, blood components that encounter an injured blood vessel will group together and form a platelet plug, through a chain reaction of blood clotting chemicals known as clotting factors.
This process also creates a protein called fibrin, which is stronger than the platelet plug. The mesh-like structures of fibrin form the actual clot. In broken vessels, fibroblasts, which are a type of cell found in connective tissue, enter the clot and increase its strength.
Anti-clotting factors in the blood balance the clotting factors to ensure that the clot does not become too large. As the injury heals, the blood clot is broken down, and it is absorbed by the body. The tough fibrin is dissolved by an enzyme known as plasmin.
When blood is flowing normally, clotting will not occur. Blood clotting processes, however, might occur abnormally within vessels or the heart. In abnormal clotting, a blood clot known as a thrombus might form in blood vessels. Strokes or heart attacks can result if a thrombus affects the blood supply to the brain or heart. Abnormal clotting is linked to atypical heartbeat and atherosclerosis.
Legs that remain still for too long, allowing blood to pool, also are at risk for forming blood clots. This condition is known as deep venous thrombosis. People who are taking extended airline flights and don’t have sufficient room to stretch their legs should take care to move about the plane frequently.
Some health conditions can cause problems with blood clotting. For example, in hemophilia, a person who has this condition might be subject to excessive bleeding. Another condition in which blood clots form slowly is von Willebrand factor deficiency. An immune disorder known as immune thrombocytopenic purpura (ITP) can also cause coagulation disorders because of reduced platelets.
Medicines such as aspirin, heparin, warfarin and clopidogrel might affect the blood clotting process. Some of these might be prescribed specifically to increase blood flow and reduce clotting. Certain supplements, such as fish oil, also can slow blood clotting.