Animation of the formation of an occlusive<unk>  in a vein. A few platelets attach themselves to the valve lips, constricting the opening and causing more platelets and red blood cells to aggregate and coagulate. Coagulation of unmoving blood on both sides of the blockage may propagate a clot in both directions. A<unk>  occurs when the hemostatic process, which normally occurs in response to injury, becomes activated in an uninjured or slightly injured vessel. A<unk>  in a large blood vessel will decrease blood flow through that vessel (termed a mural<unk> . In a small blood vessel, blood flow may be completely cut off (termed an occlusive<unk> , resulting in death of tissue supplied by that vessel. If a<unk>  dislodges and becomes free-floating, it is considered an embolus. If an embolus becomes trapped within a blood vessel, it blocks blood flow and is termed as an embolism. Embolisms, depending on their specific location, can cause more significant effects like strokes, heart attacks, or even death. 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<unk> is), and genetic or disease-related deficiencies in the blood's clotting abilities. Formation Platelet activation occurs through injuries that damage the endothelium of the blood vessels, exposing the enzyme called factor VII, a protein normally circulating within the vessels, to the tissue factor, which is a protein encoded by the F3 gene. The platelet activation can potentially cause a cascade, eventually leading to the formation of the<unk> . This process is regulated through<unk> oregulation. File:Fetal<unk> otic vasculopathy - very high mag.Micrograph showing a<unk>  (center of image) within a blood vessel of the placenta. H&E stain. File:Blausen 0088 BloodClot.Illustration depicting<unk>  formation over arterial plaque. File:Composition of a fresh<unk> .Composition of a fresh<unk>  at microscopy, showing nuclear debris in a background of fibrin and red blood cells.
Thrombus
Thrombosis
Abscess
Enema
Thrombocythemia
Platelet plug
Embolus
Hernia