What is a Blood Clot?

A blood clot is a coagulated mass of blood cells and other blood components. It plugs any damaged area of the vessel wall and maintains the integrity of the blood vessel by preventing blood from leaking out.

A host of factors come into play in blood clotting (coagulation). When an area of the vessel lining known as the endothelium is damaged, platelets in the blood attach to his area. It then attaches fibrinogen which are long fibers that help to form a mesh network. Fibrinogen is converted to fibrin by the action of the enzyme thrombin. The platelets adhere to each other to form a tight plug and the fibrin becomes tightly woven to form a clot (platelet plug).

Once the damaged area is sealed, the lining of the vessel wall regrows and the clot dissolves. The integrity of the blood vessel is restored and there is no threat of losing blood at this site.

Sometimes a blood clot forms inside a vessel and continues to grow by trapping red and white blood cells, with further platelet aggregation and fibrin deposition. This affects the flow of blood in the vessel and can break off and lodge elsewhere in the vascular system (embolus). This is known as a thrombus. Technically, a thrombus is a blood clot but in thrombosis, the process of clotting goes beyond what is necessary to seal off a damaged vessel wall.

Article reviewed by Dr. Greg. Last updated on July 5, 2010