The process of blood solidification. Blood clotting is important in stemming bleeding from damaged blood vessels. However, blood clots can also form inside major blood vessels leading to a stroke or myocardial infarction.
When damaged a blood vessel constricts immediately to reduce blood flow to the area. The damage sets off a series of chemical reactions, leading to the formation of a clot to seal the injury. First off platelets around the injury are activated, become sticky and adhering to the blood vessel wall. The activated platelets then release chemicals that, in turn activate coagulation factors. These factors together with vitamin K, act on fibrinogen, a substance found in blood, converting it to fibrin. Strands of fibrin form a kind of mesh work, which traps red blood cells to form a clot.
There are a few anticlotting mechanisms that stop the formation of unwanted blood clots. These mechanisms include plasmin, which breaks down fibrin and prostacyclin, which prevents platelet aggregation. Blood flow washes away active coagulation factors; and the liver deactivates excess coagulation factors.
Defects in blood clotting can lead to or result in bleeding disorders. Excessive clotting, or thrombosis, may be due to an inherited increase or defect in a coagulation factor; a decrease in the level of enzymes that inhibit coagulation; the use of oral contraceptives; or sluggish blood flow through a particular area. Treatment is most commonly with anticoagulant drugs such as warfarin or heparin according to allopathic medicine.