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Platelets/ megakaryocytes

Platelets/ megakaryocytes. Normal value: 1.5-4 lakh cells/cumm of blood. Size : 1.5-3 microns Life span : 8-12 days Destruction by spleen. Structure of platelets. Small anucleate cells

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Platelets/ megakaryocytes

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  1. Platelets/ megakaryocytes

  2. Normal value: 1.5-4 lakh cells/cumm of blood. Size : 1.5-3 microns Life span : 8-12 days Destruction by spleen

  3. Structure of platelets • Small anucleate cells • Highly developed cytoskeletal system • Granulated • Extensive microtubules and microfilaments • Frequently change shape with very long thin processes extending out called filopodia.

  4. Cell membrane • Exterior glycocalyx coat • Negative charge on the surface due to sialic acid residues along with glycoproteins prevent adherence to each other and endothelium. • Open canalicular systems • Dense tubular systems • Platelet granules - alpha granules - dense granules

  5. Variations : Thrombocytosis. • Splenectomy. • After trauma: surgery ,injury ,child birth. • Adminstration of epinephrine. • Stress .

  6. Thrombocytopenia: • Bone marrow depression. • Hypersplenism • Viral infection Eg: Dengue fever. • Drug hypersensitivity

  7. Functions of platelets: • Hemostasis:Temporary platelet plug. • Blood coagulation: Release clotting platelet Factor 4, V, XI, XIII PL ,HMWK. • Clot retraction • Thrombolysis • Phagocytic function: • Storage and transport function: • Vasoconstriction Wound healing and vascular growth : Platelet derived growth factor

  8. Platelet disorder: A. Thrombocytopenia: Reduction in the platelet count secondary to some other cause. B . Idiopathic thrombocytopenia: Reduction in the number of platelets due to unknown cause. C. Thromboasthenia : Defective platelet function.

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