<prompt> Platelet adhesion to collagen occurs via: AIIMS May 2015. Nov 2013Factor VIIIFactor IXvon Willebrand factorFibronectin  <response>: Ans. c. von-Willebrand factor Ref: Robbins 9e p117,118. 8e p116-118Platelet adhesion to collagen occurs via von- Willebrand factorEndothelial injury allows platelets to contact the underlying extracellular matrix; subsequent adhesion occurs through interactions with von Willebrand factor vWF, which is a product of normal endothelial cells and an essential cofactor for platelet binding to matrix elements. -Robbin 8e p116Platelet AdhesionCertain proteins are expressed on the platelet surface that subsequently regulate collagen-induced platelet adhesion particularly under flow conditions, and include glycoprotein GP-IV, GP-V1. and the integrin-alfa2, and beta1.The GPIb-IX-V complex binds to the exposed von-Willebrand factor, causing platelets to adhere.Von-Willebrand factor--bound GPlb-IX-V promotes a calcium-dependent conformational change in the GPlIbIIIa receptor, transforming it from an inactive low-affinity state to an active high-affinity receptor for fibrinogen.Factors Promoting Platelet Aggregation ADPQ EpinephrineQ Thromboxane-A2Q Serotonin von-Willebrand factorQ FibrinogenQ ThrombospondinQ Collagen Immune complex ThrombinQ 