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platelet congregation and result in thrombosis. Prolonged bed rest—in operation and illnesses in which there is a pooling of blood in the vessels of extremities, can also result in clotformation. Eventually the clots break loose and may be carried to the pulmonary arteries. Early ambulation is, therefore, recommended in operations.
Fortunately, the body has an assortment of natural mechanism for coping with the danger of thrombosis. First of all, the inner surface of the blood vessels is extremely smooth as well as coated with a very thin film of a negatively charged protein substance which repels the clotting factor. Antithrombin, normally present in the blood, also acts to remove thrombin from the blood and inhibit clotting. Helapin, a powerfulanticoagulant is secreted into the blood by most cells of the connective tissues around the capillaries. It prevents clotting in several ways. Dicumarol and hirudin are substances not found in the body, but can be adminstered to reduce the risk of thrombo-embolism.
If an important blood vessel of the body is blocked (by a clot), the obstruction deprives body-tissues of vital supplies of oxygen and nutrients. Poisonous waste products build up in the starved tissues and if they are part of key organ, the damage that results may lead to death. Thus clearing a clot may literally be a race against death. In a healthy body clot formation and dissolution go hand in hand to some extent. One of the plasma proteins, when activated, resembles the enzyme trypsin. It literally digests a blood clot, dissolving it away.
Atherosclerosis and Arteriosclerosis
Atherosclerosis, the building up of fatty deposits in the artery walls, narrows the blood-vessel-lumen (i.e. the interior capacity), raising the blood-pressure, forcing the heart to work harder against the increased peripheral resistance and increasing the possibility of thrombosis. A progressive deposition of fatty deposits (mainly cholesterol) in the inner layer of the arteries produces hardening of the arteries
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