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A blood clot occurring on the wall of a blood vessel where the endothelium is damaged.



a clot of blood formed during the lumen of a blood vessel or in the heart. In a broader sense, extravascular clots of blood that form during bleeding, as well as clots of lymph in the lymphatics are also called thrombi.

The formation of a thrombus consists of the following stages: agglutination of platelets, coagulation of fibrinogen, agglutination of red blood cells, and precipitation of plasma proteins. Thrombi may be white, red, laminated, or hyaline. A white thrombus consists of platelets, fibrin, and white blood cells and is formed slowly during rapid blood flow, generally in arteries. A red thrombus, in which red blood cells predominate, forms rapidly during slow blood flow, generally in veins. The most common type of thrombus is the laminated thrombus, which has a layered structure and crimped surface and contains fragments of white and red thrombi. It is attached to the endothelium of a blood vessel, generally that of a vein; this differentiates it from a postmortem thrombus. A hyaline thrombus forms in blood vessels of the capillary bed and consists of a homogenized mass of protein.

A thrombus may be parietal or obstructive. A parietal thrombus forms within the heart in endocarditis and heart disease, in large arteries in atherosclerosis, and in veins in thrombophlebitis. As a parietal thrombus grows, it becomes obstructive, generally in small arteries and veins. A thrombus that grows rapidly into the lumen of a vessel is called progressive, and one that originates in cardiac insufficiency is called congestive. A thrombus that forms in aneurysms is called dilatational; one that is unattached within an atrium is called spherical. A thrombus can dissolve or can grow connective tissue, a process called organization. Thin-walled blood vessels may appear in this tissue (canalization), or calcium salts may be deposited (calcification). A thrombus may cause an embolism or may become purulent, a condition accompanied by a thrombobacterial embolism and leading to sepsis.


References in periodicals archive ?
Sometimes, blood clots form despite taking precautionary measures, so stay alert for symptoms, which include pain and swelling in the calf.
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Most people associate developing a thrombosis with flying, however we know the dangers of developing a blood clot in hospital are much higher," said Dr Graham Shortland, Executive Medical Director at Cardiff and Vale University Health Board.
Travelers flying long distances, especially flights longer than 10 hours, are subject to a very small risk of developing lower-extremity blood clots.
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However, very few are aware of the fact that prolonged immobility in the workplace also poses an immediate threat, more than doubling the risk of developing a potentially fatal blood clot.
About 70 per cent of such cases don't show any symptoms and the patient can suddenly die of the blood clot.
An inquest heard that Mr Hillock had developed a blood clot, while immobile at home for three weeks.
I believe he would have made the World Cup for the summer but we have to make sure first of all he recovers from this blood clot.
All the study participants had had recent blood clots.
The results of recent studies conducted by the World Health Organization on the hazards of travel suggest that people who sit without moving for four hours or more are doubling their risk of experiencing a blood clot.