Q.A person met with a small accident and bleeds, but very soon stops bleeding. Explain the physiological process responsible for this.

Bleeding stops due to blood clotting (coagulation): platelets aggregate and release clotting factors at the wound, activating a cascade that converts prothrombin to thrombin, which in turn converts soluble fibrinogen...

Blood clotting is a rapid enzymatic cascade that plugs a small wound with a fibrin-and-platelet clot.

When a blood vessel is injured, it first constricts (vasoconstriction) to reduce blood flow, and platelets adhere to the exposed damaged tissue/collagen at the wound site, clumping together to form a temporary platelet plug. These aggregating platelets, together with damaged tissue, release clotting factors (including thromboplastin) that trigger a cascading series of enzymatic reactions. This cascade converts the inactive plasma protein prothrombin into its active enzyme form, thrombin, in the presence of calcium ions. Thrombin then acts on the soluble plasma protein fibrinogen, converting it into insoluble fibrin, which polymerises into a mesh of fine threads across the wound. This fibrin m …