Kirvon Butler
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BIO 109

Haemostasis and blood clotting: Preventing deep vein thrombosis

The body’s ability to control the blood flow after sustaining an injury is essential to continued survival. Haemostasis is the process of blood clotting and then the dissolution of the clot after the injured tissue is repaired. Haemostasis comprises of four major events that occur in sequence following the loss of vascular integrity. 1. The first phase of the process is vascular constriction. The blood flow around the injured area is limited. 2. Next, platelets become activated by the enzyme thrombin and cluster around the injured area, forming a loose platelet plug. The protein fibrinogen is responsible for stimulating platelet clumping. Platelets clump together by binding collagen that becomes exposed after the rupture of the endothelial lining of vessels. Once activated, platelets release the nucleotide, ADP and the eicosanoid, TXA2 (both also activate additional platelets), serotonin, phospholipids, lipoproteins and other proteins important for the coagulation cascade. Along with the induced secretion, activated platelets also change their shape to assist in the formation of the plug. 3. To ensure that the initially loose platelet plug is stable, a fibrin mesh (clot) forms and encases the plug. If there are only white platelets in the plug it is called a white thrombus. If red blood cells are present it is called a red thrombus. 4. Lastly, the clot must dissolve in order for normal blood flow to continue following tissue repair. The dissolution occurs through the action called plasmin.
Deep vein thrombosis takes place when blood clots form in one or more of the deep veins in your body, usually in the legs. Deep vein thrombosis can cause leg pain or swelling, but can also occur without any symptoms.
Deep vein thrombosis can develop as a