Question

Is blood clotting formed by platelets by coming in contact with oxyen?? If yes, then why clots are not formed in the blood as blood also contains oxygen??

Answer 1

Clotting occurs when platelets release a phospholipid called platelet factor-3 at the site of an injury. Injured tissues also release a phospholipid factor called thromboplastin. These two factors combine with calcium ions and certain proteins of the blood plasma to form an enzyme prothrombinase. The prothrombinase inactivates heparin in the presence of calcium. Prothrombinase catalyzes breakdown of prothrombin into an active protein called thrombin and some small peptides. Thrombin brings about the polymerization of fibrinogen into its monomers. Later thrombin stimulates repolymerization of these monomers into long insoluble fibre-like polymers called fibrin. The long, thin and solid fibres of fibrin form a dense network upon the wound and trap blood corpuscles to form a clot.
Thus, there is no role of oxygen in blood clotting.