Some people lack the gene for the production of certain clotting factors, for example, factor VIII. They suffer from a disease called haemophilia. This is an impaired clotting mechanism which causes serious bleeding particularly in the joints. In severe cases haemophiliacs may die of internal or external bleeding. Certain clotting factors such as factor VIII can now be produced by genetic engineering and are used in the treatment of haemophilia.
Sometimes a local blood clot (thrombus) is formed on the damaged rough inner wall of the artery. This may cause blockage of the artery, a condition known as thrombosis. When the thrombus dislodges and is carried away by blood circulation, it is known as an embolus. The embolus may be trapped in the small artery where it blocks the blood flow. This condition is called embolism.
If the coronary artery is partially blocked, it can cause chest pains called angina. A total blockage, which cuts off the supply of oxygen and nutrients to the heart muscles, causes heart attack (myocardial infarction). The affected heart muscles are damaged. If only a small area of the muscle cells died, the victim can recover. Extensive heart muscle damage can cause death. A stroke occurs if there is a blockage of blood to the brain cells. Strokes are commonly caused by an embolus blocking the flow of blood to a portion of the brain.
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