There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of cross-linked fibrin protein.

This can cause a number of problems particularly affecting the alveoli in the lungs of the respiratory system resulting from reduced oxygen supply.

[3] Thrombi are classified into two major groups depending on their location and the relative amount of platelets and red blood cells.

Microclots are small clumps of blood that form within the circulation, usually as a result of a larger thrombus breaking down into smaller pieces.

[citation needed] Microclots can cause a number of problems particularly affecting the alveoli in the lungs of the respiratory system, resulting from reduced oxygen supply.

The three factors have been further refined to include circulatory stasis, vascular wall injury, and hypercoagulable state, all of which contribute to increased risk for venous thromboembolism and other cardiovascular diseases.

Causes are septicaemia, acute leukaemia, shock, snake bites, fat emboli from broken bones, or other severe traumas.

Treatment involves the use of fresh frozen plasma to restore the level of clotting factors in the blood, as well as platelets and heparin to prevent further thrombi formation.

Embolisms, depending on their specific location, can cause more significant effects like strokes, heart attacks, or even death.

[11] Some of the conditions which increase the risk of blood clots developing include atrial fibrillation (a form of cardiac arrhythmia), heart valve replacement, a recent heart attack (also known as a myocardial infarction), extended periods of inactivity (see deep venous thrombosis), and genetic or disease-related deficiencies in the blood's clotting abilities.

Anticoagulants are drugs used to prevent the formation of blood clots, reducing the risk of stroke, heart attack and pulmonary embolism.

Tissue plasminogen activator (tPA) is a different enzyme that promotes the degradation of fibrin in clots but not free fibrinogen.