BLOOD CLOTTING

When you cut your finger and it bleeds, your

body fixes it by a scab forming over theinjury.This is your blood clotting to allow the

injuryto heal by replacing the damaged cells withnew 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 plateletsin the blood stick to the wall of the damagedvessel & rupture. If the blood vessel is onlymildly damaged, the material from theruptured platelets seals the injury. If theinjury is more serious then the clottingprocess is triggered.

Steps to Clotting Process1. The ruptured platelets & the wall of the injured

blood vessel release an enzyme, thromboplastin.

2. Thromboplastin starts a series of enzyme-controlled reactions resulting in the conversion of prothrombin (plasma protein) into thrombin.

3. Thrombin, an enzyme, converts soluble plasma fibrinogen in to strands of fibrin.

4. Fibrin forms a new network of strands that trap red blood cells & platelets to form a clot.

Watch How a Blood Clot forms:

• Animation 1 • Animation 2

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.

CLOTTING PROBLEMSVarious conditions can cause the clotting system tofail: a) not enough platelets

b) lack of vitamin Kc) hemophilia

Not all clotting problems involve a failure to clot.Sometimes a clot will form in a blood vessel wherethere is no injury. These clots can even travelthrough the body. If it cuts off blood flow it can leadto death.

blood clot in brain = strokeblood clot in heart = heart attack