Chapter 6 Platelets and coagulation

Publisher Summary This chapter focuses on the participation of platelets in the coagulation process, with emphasis on the involvement of the platelet plasma membrane in prothrombin and factor X activation. Formation of a hemostatic plug at sites of vascular injury requires the participation of blood platelets. This they do by clumping together into an aggregate and by promoting efficient coagulation, which consolidates the plug with strands of fibrin. Cellular organization and integrity is required for adequate platelet function. This organization critically depends on the presence and architecture of both plasma membrane and intracellular organelles. The plasma membrane plays a crucial role in the binding of external stimuli, in the transduction of the signal into the cell, and in the execution of the platelet response. Blood platelets are formed in the bone marrow from cytoplasmic fragments of megakaryocytes. Platelets can be activated by a variety of structurally non-related compounds to execute a number of cellular responses. Among these stimulators are collagen, thrombin, epinephrine, platelet-activating factor (PAF), Ca-ionophores, immune complexes, serotonin, and arachidonic acid. Platelet plasma membrane interacts with coagulation factors resulting in increased complex formation ensuring rapid generation of thrombin.