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Published byGary Maxwell Modified over 9 years ago
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HEMOSTASIS
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Hemostasis
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a body mechanism to stop traumatic bleeding to prevent spontaneous bleeding to keep the fluidity of blood
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Vascular injury tissue thromboplastin platelet adherent vaso constriction F XII activation ADP primary platelet aggregation PF3 ADP 5 OH tryptamin TxA2 secondary platelet aggregation (semi permeable platelet plug) fibrin non permeable platelet plug
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Reactions in hemostatic process Vascular reaction primary hemostatic barrier Cellular reaction Biochemical reaction / secondary hemostatic barrier
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The role of vascular in hemostasis vaso constriction Stimulates coagulation factors and platelets Substances synthesized by endothelial cells: –von Willebrand factor –tissue plasminogen activator (t-PA) –plasminogen activator inhibitor -1 (PAI-1) –prostacyclin (PGI 2 ) –Thrombomodulin (PC activation) –Glycosaminoglycan (heparan sulphate, dermatan sulphate)
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Platelet Originated from cytoplasm of megakariocyte (fragmentation) Morphology : discoid, biconvex, Ǿ 2 – 4 μm Cytoplasm contains: granule (PF 4, thromboglobulin, platelet derived growth factor, vWF, fibrinogen, F V) Dense granule (Ca, ADP, ATP) Membrane: phospholipid bilayer, glycoprotein (receptor)
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MegakaryoblastMegakaryocytesPlatelets 1/3 of platelets: stored in spleen 2/3 of plateletes: blood circulation half-lime 3-4 days 15% use daily for haemostasis normal platelet count 140-360 x 10 9 /l The Platelets
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Morphology of platelet
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The role of platelet in hemostasis Platelet plug formation: –Platelet adherent (need von Willebrand Factor) –Platelet aggregation stimulated by ADP, thrombin, thromboxan A 2, epinephrine, collagen –Platelet release reaction (from granule and dense granule) Stabilization of the plug : platelet factor 3 (flip flop of membrane phospholipid)
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Platelet Function
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phospholipid Arachidonic acid PGG2, PGH2 Thromboxan A2 Phospholipase A2, C cyclooxygenase Thromboxan synthetase Prostacyclin Prostacyclin synthetase Aspirin
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Thromboxan A2 Stimulates aggregation Vaso constriction Prostacyclin Inhibits aggregation Vaso dilatation
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Coagulation Factors Factor IFibrinogenprecursor of fibrin Factor IIProthrombinserine protease Factor IIITissue thromboinitiate extrinsic path. plastin Factor IVCalsium ionbridge between Gla - phospholipid Factor VProaccelerinCofactor of Xa Factor VIIProconvertinserine protease Factor VIIIAnti hemophilic f.Cofactor of IXa
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Coagulation factors (cont) Factor IX Christmas factor serine protease Factor X Stuart Prower factor serine protease Factor XI Antihemophilic C serine protease Factor XII Hageman factor serine protease Factor XIII Fibrin stabilizing f. transglutaminase Prekallikrein Fletcher factor serine protease HMW kininogen Fitzgerald factor cofactor of Kall.
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Characteristic of coagulation factors GroupMemberSerumAdsorb plasma Fibrinogen group I, V, VIII, XIII absentpresent Prothrombin group II, VII, IX, Xpresentabsent Contact group XI, XII, PK, HMWK present
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Vitamin K Vit. K is required for carboxylation of glutamic acid → carboxy glutamate Vitamin K dependent protein : prothrombin, VII, IX, X, protein C, protein S, protein Z Deficiency of vit. K → PIVKA (protein induced by vitamin K absence or antagonist)
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Residue Glutamic acid (GLU) Precursor of II, VII, IX, X Precursor of II, VII, IX, X Prothrombin VII, IX, X Prothrombin VII, IX, X Residue Carboxy glutamat (GLA) carboxylase Vitamin KH2 Vitamin K epoxide Vitamin K epoxide Oral Anticoagulant Oral Anticoagulant
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Negative surfaceTissue thromboplastin Kal. PK HMWK XII XIIa XI XIa VIIaVII IX IXa Ca ++ Pf 3 VIII VIIIa X Xa Ca ++ Pf 3 V VaFibrinogen Prothrombin Thrombin Fibrin monomer Fibrin polimer XIII XIIIa Stabilized fibrin Ca ++ FPA FPB + F1.2 +
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Mechanism of coagulation factor activation
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Homeostatic mechanism Local: fibrin, blood flow Humoral: - Antithrombin - Protein C - Protein S - Heparin cofactor II - TFPI Cellular : liver cell, RES
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Antithrombin Synthesized in the liver Function : neutralize thrombin and other serine protease (XIIa, XIa, Xa, IXa, VIIa, Kallikrein,plasmin) Heparin cofactor Activities enhanced by heparin
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Mechanism of action of AT III and heparin
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Function of antithrombin
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Protein C and protein S Both are vitamin K dependent protein Thrombin with thrombomodulin as cofactor activates Protein C activated Protein C (APC) APC with Protein S as cofactor inactivates F Va and F VIIIa.
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Protein C pathway
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Tissue factor pathway inhibitor (TFPI) Function : inhibit F Xa and F VIIa Mechanism of action: –First F Xa + TFPI F Xa-TFPI complex –F Xa-TFPI complex + F VIIa-TF complex quartener complexed
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Mechanism of action of TFPI
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Fibrinolytic system
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Fibrinolysis is a physiologic response to the deposition of intra or extra vascular fibrinFibrinolysis is a physiologic response to the deposition of intra or extra vascular fibrin Function : to destroy fibrin by enzymatic processFunction : to destroy fibrin by enzymatic process Consist of :Consist of : –Plasminogen –Plasminogen Activator –Inhibitor
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Fibrinolytic system Plasmin : proteolytic enzyme, substrates : fibrin, fibrinogen, V, VIII, hormon, complement PLasminogen : proenzyme of plasmin, found in plasma and other body fluid Plasminogen activator Inhibitor
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Plasminogen activator Physiologic plasminogen activators: Tissue-type plasminogen activator (t-PA) Urinary- type plasminogen activator (u-PA) Contact-phase dependent activators: F XIIa, Kallikrein Exogen: –Streptokinase (SK) –Staphylokinase (SAK) –Vampire bat plasminogen activator
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Inhibitor of fibrinolysis system Antiplasmin: 2 plasmin inhibitor 2 macroglobulin antithrombin 1 antitrypsin TAFI Transamin Plasminogen activator inhibitor –PAI-1 –PAI-2 –PAI-3 (?)
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Coagulation and Fibrinolytic cascade
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The function of PAI-1
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The mechanism of fibrinolysis and inhibition of fibrinolysis
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Plasminogen Free plasminogen in clot PAI Plasminogen activator Plasmin Free plasmin antiplasmin in clot Fibrin FDP Fibrinogen FDP D dimer + F V, F VIII D dimer -
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Kinin kininogen XII HMWK Kallikrein XI XIIa XIa Prekallikrein Plasminogen Plasminogen Proactivator Activator Plasminogen Plasmin Complement system
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Contact activation XIa IXa + VIII APC TM TF-VIIa Xa+V IIa Fibrin Fibrinolysis TFPI TM TAFI
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