Platelets in an advanced stage of activation change from coagulation-inactive to coagulation-promoting cells. This procoagulant response is characterised by exposure of aminophospholipids, such as phosphatidylserine, to the platelet surface and by formation of microvesicles. Under specific conditions, when both signalling and adhesive platelet receptors are occupied, collagen and also thrombin are able to trigger this response. Thus, platelets express high coagulation-promoting activity only after interacting with multiple receptors.
Heemskerk, J. W. M., Siljander, P. R. M., Bevers, E. M., Farndale, R. W., & Lindhout, T. (2000). Receptors and signalling mechanisms in the procoagulant response of platelets. Platelets, 11(6), 301-306. https://doi.org/10.1080/09537100050144704