1. Dr VIKASHJunior Resident 1,PathologyIMS,BHU

2. HemostasisNormal physiological mechanism forkeeping the blood in fluid state in vascularsystem and for prevention of hemorrhage bycomplex interaction of blood vessels wall ,platelets and plasma proteins. Primary type- Platelets plugs(b/w bloodvessels and platelets) Secondary type-(Activation of coagulationfactors by a series of enzymatic activity toform fibrin clot) 3. HemostasisPurpose Ensure that coagulation mechanisms are activated when there is injury not unnecessarily activatedRestore tissue blood flow after repair of injury(fibrinolysis) 4. Hemostatic Process3 main steps Primary hemostasis: local vasoconstriction &platelet plug formationCoagulation cascade Fibrinolysis 5. Platelets Cytoplasmic fragmentation of megakaryocyte in bonemarrow Life Span- 7 to 10 days Normal Platelet Count-(150 400) 103 per mm3. 6. Hemostatic ProcessPlatelet Plug Formation vascular injury release and binding of vWF toexposed blood vessel collagen glycoprotein IB on plateletsurface membrane binds to vWF 7. Platelet Activation & Aggregationexposed endothelial surfaceplatelets exposed to collagenactivatedrelease contents of cytoplasmic granulesadenosine diphosphate (ADP) thromboxane (Tx A2)accelerates platelet vasoconstrictionaggregation/activation ADP release from platelets 8. Blood Vessels-Endothelial cellsvon Willebrand factor, Tissue factor , PAF(help in clotting)Subendothelial collagenProstacyclin(inhibit platelet aggregation),Protein C,S(Inhibit coagulation),TPA(fibrinolysis) 9. Hemostatic ProcessCoagulation Cascade to stabilize and reinforce the weak platelet plug fibrinogen fibrin 3 main steps:1. formation of prothrombin activator2. conversion of prothrombin into thrombin3. conversion of fibrinogen to fibrin 10. Coagution System 11. Coagulation Mechanism activation of clotting factors requires a phospholipid surface tissue factor (TF) extrinsic to the blood activated platelet (platelet factor 3phospholipid) intrinsic to blood vitamin-K dependent factors (II, VII, IX, X) formation of reaction complex labile factors : factors V and VIII 12. Bleeding Disorders Defect in any of the step of coagulaton system startingfrom abnormalities of blood vessels,Platelets,orCoagulation factors Symptoms are Petechie,Purpura,Ecchymoses,andmucous membrane bleeding 13. Disorder of Platelets Disorder in no-