thrombosis

[New Latin thrombōsis, from Greek, a clotting, from thrombousthai, to clot, from thrombos, clot.]

The process of forming a thrombus, which is a solid mass or plug in the living heart or vessels composed of the constituents of the blood. Thrombosis usually occurs in a diseased blood vessel, as a result of arteriosclerosis. The consequences of thrombosis include local obstruction causing both tissue death and hemorrhage. Thrombosis is a significant factor in the death of an individual affected by arteriosclerotic cardiovascular disease, malignancy, and infection. See also Hemorrhage; Infarction.

Thrombosis is usually initiated by vascular damage and consequent platelet adhesion and clumping. The process is initiated when platelets specifically adhere to the subendothelial collagen at the points of damage to the endothelium. At the same time that the platelets begin to aggregate and release products that will further promote thrombus formation, the protein factors of the blood, which help to form the insoluble meshwork of the thrombus, become activated. This latter process is known as blood coagulation. The proteins of the coagulation system, through a series of cascading reactions, eventually reach a final common pathway to form fibrin, the insoluble protein that forms the scaffolding of the thrombus. As blood flows by the thrombus, more platelets and fibrin are deposited. Red blood cells and white blood cells become entrapped in the thrombus and are integrated into its structure. See also Fibrinogen.

Once a thrombus forms, it can have one of four fates. (1) It may be digested, destroyed, and removed by proteolytic enzymes of the plasminogen-plasmin system. (2) It may continue to propagate itself and eventually occlude the vessel. (3) It may give rise to an embolus. Emboli may cause tissue damage at sites distant from the origin of the thrombus. (4) It may undergo a process known as organization. Organization helps stabilize the thrombus, and it may result in incorporation of a contracted fibrous mass into the vessel wall. See also Embolism.

Maintaining good blood flow (especially in the veins) helps prevent thrombosis. Treating hypertension and hypercholesterolemia retards atherosclerosis, which is a major cause of arterial thrombosis. Agents that interfere with platelet function, such as aspirin and fish oils, may help avoid thrombotic episodes. Anticoagulants prevent the formation of fibrin and may also be used to prevent thrombosis. If treatment can be given in the early stages of thrombosis, fibrinolytic therapy, utilizing agents that will help form plasmin, can minimize the tissue damage caused by thrombosis. See also Arteriosclerosis; Circulation disorders; Phlebitis.

Formation of blood clots in blood vessels.

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The development of a blood clot in the circulatory system. Depending on the location of the clot, the resultant loss of circulation can lead to a stroke (cerebral thrombosis) or heart attack (coronary thrombosis).

Formation, development, or presence of a thrombus.
A thrombus may form whenever the flow of blood in the arteries or the veins is impeded. If the thrombus detaches itself from the wall and is carried along by the bloodstream, the clot is called an embolus. The condition is known as embolism. Because blood normally flows more slowly through the veins than through the arteries, thrombosis is more common in the veins than in the arteries.
The effect of a thrombosis is engorgement of the obstructed vein, usually further aggravation of the thrombus formation, and edema of the local area drained by the vein. The clinical signs will depend on the location of the vessel, e.g. cerebrovascular, pulmonary.

• caudal vena cava t. — see caudal vena caval thrombosis.
• iliac t. — see iliac artery thrombosis.

Dansk (Danish)
n. - dannelse af blodprop

Nederlands (Dutch)
trombose

Français (French)
n. - thrombose

Deutsch (German)
n. - Thrombose

Ελληνική (Greek)
n. - (παθολ.) θρόμβωση

Italiano (Italian)
trombosi

Português (Portuguese)
n. - trombose (f)

Русский (Russian)
(мед.) тромбоз

Español (Spanish)
n. - trombosis

Svenska (Swedish)
n. - blodpropp, trombos

中文（简体）(Chinese (Simplified))
血栓症

中文（繁體）(Chinese (Traditional))
n. - 血栓症

한국어 (Korean)
n. - 혈전증

日本語 (Japanese)
n. - 血栓症

العربيه (Arabic)
‏(الاسم) الخثر‏

עברית (Hebrew)
n. - ‮פקקת, תרומבוזה, תקריש‬

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