1. Platelets Presents to you by ABOUT DISEASE.CO TEAM

2. Definition

3. Platelets

4. Size: 1 – 4 Micro meter in diameter Normal Count: 1, 50000 – 300,000 / cu mm or micro liter Live span: 10 days Platelet membranes contain receptors for  Collagen  ADP  Vessel wall Von Willebrand factor  Fibrinogen  Glycoprotein

5. Platelets cytoplasm contain  Actin  Myosin  Thrombasthenin  Glycogen  Lysosomes  Granules I.Dense granules Contains non protein substances e.g. Serotonin, ADP, Ca and other nucleotides. II. Alpha granules: Secrete proteins e.g. Clotting factors, platelet derived growth factor (PDGF), Von Willebrand factor.

6. Regulation of Platelet Production  Thrombopoietin  Erythropoietin  Adrenaline  Injury  Hypoxia  Smoking

7. Thrombocytopenia Decreased Number of platelets in the blood Causes. 1.Idiopathic 2.Secondary a.Pancytopenia b.Increased destruction of platelets c.Splenomegaly d.Leukemia

8. Thrombocytosis Increase no of platelets in the blood Causes. 1.After acute haemorrhage 2.Splenectomy 3.Polycythemia vera

9. Hemostasis “Arrest of bleeding” is called hemostasis. It involves three steps 1.Vascular spasm a.Inherent vascular response b.Sympathetically induced vasoconstriction 2.Formation of platelet plug a.Platelet adhesion b.Platelet activation c.Platelet aggregation 3.Clot formation a.Intrinsic system b.Extrinsic system

10. Activated Platelets

11. Platelet plug Formation

12. Factors involved in Platelet Function

13.  Whenever the vessel is damaged, the net result is formation of prothrombin activator.  Prolthrombin activator is formed in two ways a.The extrinsic pathway b.The intrinsic pathway

15. Intrinsic Pathway for initiating Clotting Intrinsic pathway

16. Extrinsic Pathway for initiating Clotting Extrinsic Pathway

18. Erythrocytes trapped in the fibrin meshwork of a clot (Clot formation)

19. Roles of Thrombin

20. Concurrent Platelet Aggregation and Clot Formation

21. Hemostasis

22. Factors involved in Clotting

23. Role of Factor XII

24. Fibrinolytic system Plasminogen Activator Plasminogen Plasmin Fibrin Fibrin Degradation Products FDPs.  Prevent platelet aggregation  Inhibit thrombin formation  Prevent fibrin polymerization Plasmin also digests factors I,II,V, VIII and XII.

25. Endogenous factors involved in Fibrinolysis and Anticoagulation

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