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platelet function:

platelet function:

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platelet function:

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  1. platelet function: 1- Adhesion — the deposition of platelets on the . subendothelial matrix  2 - Aggregation — platelet-platelet cohesion  3- Secretion — the release of platelet granule proteins  4- Procoagulant activity — the enhancementof thrombingeneration

  2. Platelet secretion : Platelets secrete a variety of substances from their granules upon cell stimulation: 1-  ADP and serotonin. 2- Fibronectin and thrombospondin.3-Fibrinogen is released from platelet alpha granules.4-Thromboxane A2, a prostaglandin metabolite, promotesvasoconstrictionand furtherplatelet aggregation.5-Growth factors, such as platelet-derived growth factor (PDGF), have potent mitogenic effect on smooth muscle cells. The release of PDGF

  3. Causes of reactive thrombocytosis: -Hemorrage - Surgery - Trauma - Iron deficiency anemia - Splenoctomy - Infection - Malignant disease - Inflamatory disease

  4. ‍Cause of Thrombocytopenia: 1 1- Decrease Marrow production: Marrow failure: AA. Marrow infiltration :leukemia , Myelidysplasia, Fibrosis…. Marrow depression: Iradiation,Chemotherapy Selective BM depression:ethanol, drugs induced Nutritional deficiency: megaloblastic anemia. Hereditary causes: Fanconi”s anemia congenital megacariocytic hypoplasia.

  5. 2 ‍Cause of Thrombocytopenia: 2- Increased destruction of platelets: Immune: ITP , SLE , CLL , NHL, CVD. Drud-induced: Heparin,Gold, Quinidine, Penicillins, cimetidine, digoxin. Infection : HIV , Other Viruses , Malaria. Post Transfusion purpura. Neonatal purpura (isoimmune). Non-immune: DIC , TTP , UHS , Congenital / acquired heart disease, Cardiopulmonary bypass , Kasabach-Merritt syndrome. Hereditary causes: Fanconi”s anemia congenital megacariocytic hypoplasia.

  6. Endothelial cell Coagulation Properties Procoagulant Anti-Coagulant Vasodilation ADP ase Heparin Sulfate Nitric oxide Prostacyclin Thrombomodulin Tissue factor pathway inhibitor Tissue Plasminogen activator Collagen Factor VIII Fibronectin Integrins P-endothelial cell adhesion molecule-1 Selectin-E Selectin-P Von Willebrand f. Vasoconstriction

  7. Screening Hemostasis Assays CBC ,PBS Thrombocytopenia, Thrombocytosis , Giant P PT Vit K deficiency ,Liver d. DIC , VII ,V , IX deficiency and Factor inhibitor. PTT Heparin , DIC , Lupus anticoagulant , vWD XI, IX ,V, X, XII, HMWK , PK , factor inhibitor. TTHeparin, DIC , Hypofibrinogenemia , Dysfibrongenemia Bleedig T. Aspirin , Thrombocytopenia , vWD , Storage pool disease Mixing Study Abnormal clotting time corrects w ith a deficiency dose not correct with an inhibitor.

  8. Drugs Affecting Platelet Strong Inhibitors Moderate Inhibitors Weak Inhibitors Alcohol Hitroglycerin Nitroprusside Aspirin Abciximab (anti gpIIb/IIIa) Ticlopidine (anti ADP) NSAFD Antibiotics Penicillins cepholosporins nitrofurantoin Dextran Fibrinolytics Heparin Hetastrach

  9. Classification of congenital disorders of platelet function 1- Disorders of adhesion: Von Willebrand disease bernared-Soulier syndrome 2- Disorders of aggregation: Congenital afibrinogenemia Glansmann thrombasthenia 3- Disorders of platelet secretion: a- Granules abnormality Storage pool deficiency Quebec platelet disordes b- Primary secretion defects reseptor defects Gaq deficiency Phospholipase C-B2 deficiency Defect in Ca++ mobilization Defect in protein phosphorylation (pleckstrin) c- Abnormalities in arachidonic acid pathways

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