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  • 2. HAEMOSTASISRefers to the complicated chemical interplay thatmaintains blood viscosity, or thickness.Blood disorders occur when haemostasis falls outof balance.If blood becomes too thin, it loses the ability toform the blood clots that stop bleeding.When blood becomes too thick, the risk of bloodclots developing within the blood vessels risescreating a potentially life-threatening condition.
  • 3. Platelet Formation (thrombocytopoiesis)Myeloid Stem CellsMegakaryoblastsMegakaryocytesPlatelets(thrombocytes)fragmentation
  • 4. PLATELETSPlatelets are produced in bone marrow by a process knownas thrombopoiesis. They are formed in the cytoplasm of the megakaryocyte (avery large cell).The cytoplasm of the megakaryocyte fragments at the edgeof the cell.This is called platelet budding.Megakaryocytes mature in about 10 days, from a large stemcell, the megakaryoblast.
  • 5. PLATELET NUMBERS• Among all the formed elements, platelets are thesmallest.They are estimated to be 150,000 –450,000 per cubicmm.• Their half life is around 10 days.
  • 6. Platelets Formation
  • 7. PLATELET FUNCTIONSThey play a role in:-Blood coagulation Formation of plugs Prevention of blood loss
  • 8. HEMOSTASIS – STOPPING BLOOD LOSS• Three stages– Vascular Spasm– Platelet plug formation– Clotting (coagulation)• Vascular spasm– Muscles in cut vessels constricts– Blood loss is immediately reduced– Clotting factors concentrate faster
  • 9. Hemostasis• Platelet plugformation– Platelet adhesion– Platelet releasereaction– Platelet aggregation
  • 11. CLOT FORMATION• Clot consists of a gel of fibrin and trappedformed elements• Clot closes cut vessel• When clot separates from plasma, remainingfluid is serum• Clotting process called coagulation
  • 12. Coagulation & Clot Stabilization• Prothrombin• Ca++• Fibrinogen• Fibrin• Polymerization
  • 13. CLOTTING FACTOR IN THE BLOODCLOTTING FACTOR SYNONYMSFibrinogen Factor IProthrombin Factor IITissue factor Factor II, tissuethromboplastinCalcium Factor IVFactor V Proaccelerin, labilefactor, Ac-globulin(AC-G)Factor VII Serum prothrombinconversion, accerator(SPLA) Proconvertinstable factor
  • 14.  Factor VIII Antihaemophilic factor (AHF)Antihaemophilic globulin (AHG) Factor IX Plasma thromboplastincomponent (PTA); Christmasfactor, Antihaemophilic factor B Factor X Stuart factor, stuart-prower factor Factor XI plasma thromboplastin antecedent(PTA), Antihaemophilic C Factor XII Hageman factor Factor XIII Fibrin stabilizing factor Prekallikrein Fletcher factor High molecular wt. Fitzgerald factor Kininogen (HWWK) Platelets
  • 15. Blood clotting occurs in three stagesStage 1.Stage 2.Stage 3.Formation of prothrombinaseFormation of thrombinFormation of fibrin plug (clot)
  • 16. BLOOD CLOTTING DIAGRAMSeveral clotting factors releasedfrom damaged tissues, vessel walland plateletsProthrombinaseCa2+Prothrombin ThrombinFibrinogen Fibrin(clot)ThrombinCa2+
  • 17. • Vitamin K needed to form four ofthe clotting factors• Within 30 minutes platelets begin toretract the clot by pulling edges ofcut vessel together
  • 18. FIBRINOLYSISIs the process where a fibrin clot, the product ofcoagulation, is broken down.Its main enzyme, plasmin, cuts the fibrin mesh atvarious places, leading to the production of circulatingfragments that are cleared by other proteinases or bythe kidney and liver.
  • 19. CLOT DISSOLVING• As repair of a cut or damaged vessel proceeds,a series of enzyme catalyzed reactions calledfibrinolysis slowly dissolves the clot• An enzyme called tissue plasminogenactivator catalyzes the conversion of inactiveplasminogen enzyme to active plasmin• Active enzyme catalyzes the dissolving of clot
  • 21. CLOT DISSOLVING DIAGRAMPlasminogen plasminTissue plasminogen activator
  • 22. INTRAVASCULAR CLOT• Intravascular clot – clot within closed vessel• Damaged vessel lining or slowing of blood flowPlatelets aggregate and release clotting factors• Resulting clot called a thrombus• Moving piece of the clot is an embolus• Clot moves downstream and blocks smallervessel embolism• May cut off blood supply to organ
  • 23. ANTICOAGULANTS• Chemicals that decrease or prevent blood clottingare called anticoagulants• Heparin is administered medically and it occursnaturally in our bodies. It works by decreasingthrombin production• Coumadin (warfarin) is effective as a long-termanticoagulant. It is an antagonist of vitamin K.• EDTA and CPD are used in blood banks to keepthe donated blood from clotting. They both workby tying-up and removing calcium.
  • 24. Dissolving the Clot and Anticoagulants
  • 25. Coagulation and DiseaseHemophiliaCardiovascular DiseasesKey problem – clots block undamaged bloodvesselsAnticoagulants prevent coagulationKeep platelets from adheringPrevent fibrin coagulation"Clot Busters": Prevent further clottingSpeed fibrinolysisLimit tissue damage (heart, brain…)
  • 26. HEMOPHILIA–Inherited clotting disorder due to a deficiency in a clottingfactor.–Hemophilia is perhaps the best known of the bleedingdisorders.–Hemophilia is a genetic disorder caused by mutations of geneson the X chromosome.–Because the mutated gene is recessive, the majority ofhemophiliacs are male.
  • 27. Von Willebrands Disease Von Willebrands disease is the most common ofthe inherited bleeding disorders, includinghemophilia. Von Willebrands disease affects up to onepercent of the population, and may be found in both sexes (as opposed tohemophilia, which primarily affects males). Von Willebrands factor is a protein that allowsplatelets to form temporary plugs at sites of bloodvessel injury: Defects in von Willebrands factor, impair theability of platelet cells to cling to an injury andform a plug.
  • 28. THROMBOCYTOPENIAThrombocytopenia occurs when platelet cells fall toabnormally low levels, impairing coagulation.Leukemia, lymphoma, and some other cancers areknown to cause thrombocytopenia. Cases of thrombocytopenia have also occurred due toheparin, a blood thinning medication.
  • 29. LIVER DISORDERSLiver cirrhosis interferes with the livers ability toproduce vital proteins, including coagulation factors.Low levels of coagulation factors in turn may lead tobleeding disorders.
  • 30. THE END“Our greatest gloryis not in neverfailing but in risingup every time wefail.”Ralph WaldoEmerson