CHAPTER 13 13 Biomaterials and Thrombosis Introduction: Overview of Hemostasis -Biomaterials Interaction via protein coats ---- blood coagulation c y ---- Hemostatic mechanism vascular constriction / platelet plug / blood coagulation (throm Role of Platelets 1 Platelet Characteristics and Functions ucleated fragment of megakaryocyte (no proliferation) hondria, ER, Golgi nule: platelet factors, b-thromboglobulin, fibrinogen, factor V and granule: ADP, Calcium, serotonin omal granules: hydrolytic enzymes let plug formation / activation of blood coagulation cascade
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CHAPTER13 Biomaterials and Thrombosis 13-1 Introduction: Overview of Hemostasis Blood-Biomaterials Interaction via protein coats ---- blood coagulation.
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CHAPTER
1313Biomaterials andThrombosis
13-1 Introduction: Overview of Hemostasis Blood-Biomaterials Interaction via protein coats ---- blood coagulation controlInjury ---- Hemostatic mechanism
13-2 Role of Platelets 13.2.1 Platelet Characteristics and Functions Non-nucleated fragment of megakaryocyte (no proliferation) Mitochondria, ER, Golgi -granule: platelet factors, b-thromboglobulin, fibrinogen, factor V and VIII Dense granule: ADP, Calcium, serotonin Lysosomal granules: hydrolytic enzymes
Platelet plug formation / activation of blood coagulation cascade
13.2.2 Platelet Activation (1)Means of activation collagen, von Willerbrand factor (vWF), proteins on biomaterials (2) Sequelae
activated platelets ---- ECM adhesion --- platelet stimulation and coagulationplatelet aggregation with fibrinogen (GPIIb/IIIa) platelet plug formation --- localized blood coagulation PL memb. of platelet --- factor X activation --- thrombin activation
Platelet Activation
13-3 Coagulation Cascade intrinsic pathway
HMWK, prekallikrein, factor XI (proteolysis by factor XII) positive feedback
extrinsic pathway tissue factor from macrophage and endothelial cells
common pathway thrombus (attached through fibronectin)
-carboxyglutamate with vit. K
13-4 Means of Limiting Clot Formation (1) Physiologic factors
normal blood flow surface (membrane) by activated platelets or platelet fragments
(2) Soluble and insoluble biochemical factors a) heparin/antithrombin III (ATIII) complex b) 2-macroglobulin c) thrombomodulin on the endothelial surface
thrombin sequestration --- protein C activation --- V & VIII inactivation d) clot dissolution process (fibrinolysis)