BLOOD CLOTTING

When you cut your finger and it bleeds, your body fixes it by a scab forming over the injury. This is your blood clotting to allow the injury to heal by replacing the damaged cells with new healthy cells. CLOTTING is the solidification of blood at the site of an injured blood vessel.

THE CLOTTING PROCESS When a blood vessel is injured, the platelets in the blood stick to the wall of the damaged vessel & rupture. If the blood vessel is only mildly damaged, the material from the ruptured platelets seals the injury. If the injury is more serious then the clotting process is triggered.

Steps to Clotting Process The ruptured platelets & the wall of the injured blood vessel release an enzyme, thromboplastin. Thromboplastin starts a series of enzyme-controlled reactions resulting in the conversion of prothrombin (plasma protein) into thrombin. Thrombin, an enzyme, converts soluble plasma fibrinogen in to strands of fibrin. Fibrin forms a new network of strands that trap red blood cells & platelets to form a clot.

The clot stops the bleeding, contracts & hardens The clot stops the bleeding, contracts & hardens. In time the wound is repaired by the growth of cells that replace the damaged cells. When healing is completed, plasmin is activated & it dissolves the clot. Watch How a Blood Clot forms: Animation 1 Animation 2

CLOTTING PROBLEMS Various conditions can cause the clotting system to fail: a) not enough platelets b) lack of vitamin K c) hemophilia Not all clotting problems involve a failure to clot. Sometimes a clot will form in a blood vessel where there is no injury. These clots can even travel through the body. If it cuts off blood flow it can lead to death. blood clot in brain = stroke blood clot in heart = heart attack