explain the mechanism of blood clotting?

Blood clotting helps for the excessive loss of blood from an injury caused to the body. It is initiated by platelets. Thromboplastin is a lipoprotein plays a major role in blood clotting.

Clot formation occurs in three steps.

1. Thromboplastin helps in the formation of prothrombinase enzyme. This enzyme inactivates heparin and it also converts the inactive prothrombin into active thrombin. Calcium ions helps for these changes.
2. Thrombin acts as a proteolytic enzyme to separate two peptides from the soluble fibrinogen molecule to form insoluble fibrin.
3. The fibrin polymerizes to form long, sticky fibres. The fibrin threads form a fine network over the wound and tap blood cells to form a crust – the CLOT.

Clot is formed in about 2 – 8 minutes and seals the wound and stop bleeding.