Thrombosis is the formation of a clot within a blood vessel. If blood vessels have been damaged by inflammation (from the spread of infection in the surrounding tissues) or if their walls are thickened and rough from arteriosclerosis, clotting may start within the vessel while the blood is still circulating through it. Very soon the clot becomes piled up on the walls of the vessel and the tube becomes completely blocked. Once this clotting process has started it spreads rapidly up and down the vessel, blocking the mouths of the little branches, and consequently the blood how to or from the part affected becomes completely obstructed. If it is an artery which is blocked by this process, gangrene may supervene very rapidly. Arterial thrombosis occurs frequently in the coronary arteries of the heart: the heart muscle is deprived of oxygen and the patient collapses; if the clotting extends to one of the bigger vessels of the coronary circulation, the patient dies. If a vein becomes affected and arterial blood is still being pumped into the part, the tissues become greatly swollen and painful.
Venous thrombosis occurs perhaps most commonly in the veins of the leg following operation, leading to the formation of an oedematous leg which is called 'white leg'. If part of the clot within the vessel becomes detached and carried on into the circulation, it is known as an ' embolus', and will be carried to distant parts, blocking smaller vessels. Blood emboli travelling in the venous circulation pass through the right side of the heart into the pulmonary artery and thence into the smaller arterioles of the lungs. If a large pulmonary artery is blocked this condition of pulmonary embolism produces sudden death. The area of the lung which has been deprived of its blood supply is an infarct. A small infarct is compatible with life. The surrounding area of lung becomes inflamed and an area of pleurisy develops. Research Thrombosis
Abbreviations
Medicine
Research Thrombosis