Thrombus
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{{redirect|Clot}}
[[Image:Blood clot diagram.png|thumb|300px|Blood clot diagram.]]
A '''thrombus''', or '''blood clot''', is the final product of the [[blood coagulation]] step in [[hemostasis]]. It is achieved via the aggregation of [[platelets]] that form a platelet plug, and the activation of the humoral [[coagulation]] system (i.e. clotting factors). A thrombus is [[physiology|physiologic]] in cases of [[injury]], but [[pathology|pathologic]] in case of [[thrombosis]].
Specifically, a thrombus is a blood clot in an intact blood vessel. A thrombus in a large blood vessel will decrease blood flow through that vessel. In a small blood vessel, blood flow may be completely cut-off resulting in death of tissue supplied by that vessel. If a thrombus dislodges and becomes free-floating, it is an [[Embolism|embolus]].
Some of the conditions which elevate risk of blood clots developing include [[atrial fibrillation]] (a form of [[cardiac arrhythmia]]), heart valve replacement, a recent [[myocardial infarction|heart attack]], extended periods of inactivity (see [[deep venous thrombosis]]), and genetic or disease-related deficiencies in the blood's clotting abilities.
Blood clot prevention reduces the risk of stroke, heart attack and [[pulmonary embolism]]. [[Heparin]] and [[warfarin]] are often used to inhibit the formation and growth of existing blood clots; they are able to decrease blood coagulation by inhibiting vitamin K epoxide reductase, an enzyme that recycles oxidated vitamin K to its reduced form after it has participated in the carboxylation of several blood coagulation proteins, mainly prothrombin and factor VII.
[[Rudolf Virchow|Virchow's]] [[Virchow's triad|Triad]] describes the conditions necessary for thrombus formation:
# Changes in vessel wall morphology (e.g. trauma, [[atheroma]])
# Changes in blood flow through the vessel (e.g. [[valvulitis]], [[aneurysm]])
# Changes in blood composition (e.g. [[leukaemia]], hypercoagulability disorders)
Disseminated intravascular coagulation ([[DIC]]) involves widespread microthrombi formation throughout the majority of the blood vessels. This is due to excessive consumption of coagulation factors and [[fibrinolysis]] using all of the body's available [[platelets]] and clotting factors. The end result is ischaemic necrosis of the affected tissue/organs and spontaneous bleeding due to the lack of clotting factors. Causes are [[septicaemia]], acute [[leukaemia]], [[Shock (medical)|shock]], snake bites or severe trauma. Treatment involves the use of fresh, frozen plasma to restore the level of clotting factors in the blood.
==See also==
* [[Embolism]]
* [[Thrombolysis]] ("Destruction of clot")
* [[Thrombogenicity]] (the tendency to clot)
* [[Partial knee replacement]]
==External links==
{{Wiktionarypar|thrombus|clot}}
*[http://www.med-help.net/BloodClot.html Treatment and Symptoms of Blood Clots] -- [http://www.med-help.net Med-Help.net], Medical Information Resource, 1999
*[http://www.natfonline.org/ North American Thrombosis Forum] - NATF is a nonprofit organization dedicated to promoting thrombosis research, prevention and education, public policy, and advocacy outreach.
*[http://www.pharmacyka.com/research/Muscle_Relaxing_Drugs_Can_Reduce_Lethal_Blood_Clots-98.html Muscle Relaxing Drugs Can Reduce Lethal Blood Clots]
* [http://www.planetark.com/dailynewsstory.cfm/newsid/44436/story.htm Air Pollution Triggers Blood Clots - US Study].
[[Category:Hematology]]
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