Blood platelets are the most important cells in the body which contribute to hemostatic mechanism. These contain three types of granules: alpha granules, dense granules and lysosomes.
When a tissue injury or a cut occurs in the body, then the dense granules of platelets become activated ———–> they contain Calcium and ADP ———–> released ————> ADP activates other platelets to release more ADP and calcium————> now the platelet changes its shape from disc shape to spherical———-> pseudopodia extended in platelets ——-> the alpha and dense granules move to the surface of platelet membrane ———-> fuse with the membrane ————> release their contents into the blood (alpha granules contain blood clotting factors like fibrinogen) —————-> At this time lysosomes digests the spent proteins of the platelet cell ———-> all these activated platelets adhere to the site of injury in blood vessel ———-> formation of platelet plug with the help of thrombin ———–> enzyme mediated reactions result in formation of fibrin from fibrinogen———> platelet plug replaced by fibrin (blood clot).