QS Study

The process by which soluble fibrinogen is converted into insoluble fibrin and forms clots are known as coagulation. Coagulation involves a cellular (platelet) and protein (coagulation factor) component. It is the process by which blood changes from a liquid to a gel, forming a blood clot.

Blood does not coagulate in the vessel because-

(A) Endothelial surface factor

  • The smoothness of the endothelium: Prevent contact activation of the intrinsic dotting system.
  • A Layer of glycocalyx: a Monocellular layer of glycocalyx repels the clotting factors and platelets, prevent clotting.
  • Thrombomodulin: Slows the clotting process and activates protein C, that acts as an anticoagulant by binding with thrombin.

Fig: Blood Vessel

(B) A speed of Blood flow

Blood flows with constant speed in the blood vessels, thus prevent intra vascular coagulation of blood.

(C) Presence of natural anticoagulant

  • Heparin: It combines with antithrombin and increases it’s activity.
  • Antithrombin III: Removes the thrombin from the blood and thus prevent fibrinogen to convert into fibrin.
  • α2 macroglobulin: Binds to several coagulation factors and prevent blood clotting.
  • Protein C: It is activated Va and VIIIa.

(D) An absence of tissue thromboplastin – It prevents intravascular coagulation.