Describe the mechanism of blood coagulation or blood clotting

- When an injury occurs, there is bleeding from the wound for sometime, but soon

the blood stops flowing out. This is because blood exhibits a mechanism called blood coagulation or clotting, to prevent excess loss of blood from the body.

- A clot or coagulum which consist of a network of threads called fibrins in which

dead and damaged formed elements of blood are trapped.

- Fibrins are formed by the conversion of inactive fibrinogens in the plasma by the enzyme thrombin.

- Thrombins, in turn are formed from another inactive substance present in the plasma called prothrombin.

- Calcium ions are necessary for both the above steps in coagulation.

- The blood clot seals the injured blood vessel and thereby bleeding stops.