BLOOD CLOTTING AND IT'S PREVENTION

 

INTRODUCTION: Clotting should take place to stop bleeding, but too much clotting would obstruct vessels and interfere with normal circulation of blood. Clots do not usually form in intact vessels because the endothelium is very smooth and repels the platelets and clotting factors. If the lining becomes roughened, as happens with the lipid deposits of atherosclerosis, a clot will form.

HEPARIN AND BLOOD COAGULATION: Heparin, produced by basophils, is a natural anticoagulant that inhibits the clotting process. The liver produces a globulin called antithrombin, which combines with and inactivates excess thrombin. Excess thrombin would exert a positive feedback effect on the clotting cascade, and result in the splitting of more prothrombin to thrombin, more clotting, more thrombin formed, and so on. Antithrombin helps to prevent this, as does the fibrin of the clot, which adsorbs excess thrombin and renders it inactive. All of these factors are the external brake for this positive feedback mechanism.  Together they usually limit the fibrin formed to what is needed to create a useful clot but not an obstructive one.

THROMBOSIS: Thrombosis refers to clotting in an intact vessel; the clot itself is called a thrombus. Coronary thrombosis, for example, is abnormal clotting in a coronary artery, which will decrease the blood (oxygen) supply to part of the heart muscle. An embolism is a clot or other tissue transported from elsewhere that lodges in and obstructs a vessel.

DISSOLVING CLOTS: Abnormal clots may cause serious problems in coronary arteries, pulmonary arteries, cerebral vessels, and even veins in the legs. However, if clots can be dissolved before they cause death of tissue, normal circulation and tissue functioning may be restored. One of the first substances used to dissolve clots in coronary arteries was streptokinase, which is actually a bacterial toxin produced by some members of the genus Streptococcus. Streptococcus

Streptokinase did indeed dissolve clots, but its use created the possibility of clot destruction throughout the body, with serious hemorrhage a potential consequence. Safer chemicals called third-generation thrombolytics are now used. In a case of coronary thrombosis, if a thrombolytic can be administered within a few hours, the clot may be dissolved and permanent heart damage prevented. The same procedure is also used to prevent permanent brain damage after strokes (CVAs) caused by blood clots.

RELATED;

1. STROKE  

2. STREPTOKINASE  

3. THE COAGULATION CASCADE

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