Thrombocyte Physiology by Dr.M.Anthony David MD

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Thrombocyte Physiology by Dr.M.Anthony David MD

  1. 1. THROMBOCYTES: PLATELETS By Dr.M. Anthony David, MD Professor of Physiology NOMAD:2006:BP:Thrombocytes
  2. 2. THROMBOCYTES: INTRO <ul><li>Normally 1.5 - 4.0 Lakhs/Cu.mm in blood. </li></ul><ul><li>Are 2 – 4 µ in diameter; smallest blood cells. </li></ul><ul><li>Developed from giant cells called Megakaryocytes. </li></ul>NOMAD:2006:BP:Thrombocytes
  3. 3. NOMAD:2006:BP:Thrombocytes
  4. 4. THROMBOCYTES: STRUCTURE <ul><li>Spherical, oval, or rod-shaped colorless bodies. </li></ul><ul><li>Diameter is between 2 to 4 μ . </li></ul><ul><li>Normally under Electron Microscopy they appear as: </li></ul><ul><ul><li>Flattened discs </li></ul></ul><ul><ul><li>Having a cell membrane </li></ul></ul><ul><ul><li>And a Cytoplasmic matrix. </li></ul></ul><ul><ul><li>Microtubules encircle the thrombocyte just below it’s surface membrane. </li></ul></ul>NOMAD:2006:BP:Thrombocytes
  5. 5. <ul><li>Do not have nuclei. </li></ul><ul><li>Cannot reproduce. </li></ul><ul><li>But behave functionally as whole cells. </li></ul><ul><li>Cytoplasm includes active proteins such as: </li></ul><ul><ul><li>Actin. </li></ul></ul><ul><ul><li>Myosin. </li></ul></ul><ul><ul><li>Thrombesthenin. </li></ul></ul>THROMBOCYTES: STRUCTURE NOMAD:2006:BP:Thrombocytes
  6. 6. <ul><li>Cell Organelles in thrombocytes include: </li></ul><ul><ul><li>Lysosomal granules. </li></ul></ul><ul><ul><li>Dense bodies: about 50 – 100 in number. </li></ul></ul><ul><ul><li>Mitochondria & Enzyme systems which produce: </li></ul></ul><ul><ul><ul><li>ATP </li></ul></ul></ul><ul><ul><ul><li>ADP </li></ul></ul></ul><ul><ul><li>Enzyme systems producing: </li></ul></ul><ul><ul><ul><li>Prostaglandins – Local hormones. </li></ul></ul></ul>THROMBOCYTES: STRUCTURE NOMAD:2006:BP:Thrombocytes
  7. 7. <ul><ul><li>Fine Glycogen granules. </li></ul></ul><ul><ul><li>Microvesicles. </li></ul></ul><ul><ul><li>Microtubules. </li></ul></ul><ul><ul><li>Filaments. </li></ul></ul><ul><ul><li>Granules: </li></ul></ul><ul><ul><ul><li>Dense: Serotonin, ADP etc. </li></ul></ul></ul><ul><ul><ul><li>ά -granules: Clotting factors such as: </li></ul></ul></ul><ul><ul><li>Fibrin Stabilizing Factor ( FSF ) Factor XIII </li></ul></ul><ul><ul><li>PDGF : Platelet Derived Growth Factor </li></ul></ul>THROMBOCYTES: Structures within NOMAD:2006:BP:Thrombocytes
  8. 8. <ul><li>Internal Membranous systems: </li></ul><ul><ul><li>Open Canalicular System: </li></ul></ul><ul><ul><ul><li>Spongelike invaginations </li></ul></ul></ul><ul><ul><ul><li>Provide multiple channels for: </li></ul></ul></ul><ul><ul><ul><ul><li>Taking up Calcium ions </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Secreting granule contents. </li></ul></ul></ul></ul><ul><ul><li>Dense Tubular System: </li></ul></ul><ul><ul><ul><li>Channels of S.E.R. </li></ul></ul></ul><ul><ul><ul><li>Serves as an intracellular store for Calcium ions. </li></ul></ul></ul>THROMBOCYTES: STRUCTURE NOMAD:2006:BP:Thrombocytes
  9. 9. Platelet Physiology <ul><li>Have a half life of 8 – 12 days. </li></ul><ul><li>Eliminated from circulation by the Tissue Macrophage system. </li></ul><ul><li>Thrombocytes are active structures. </li></ul><ul><li>About half of them are removed by the Macrophages in the Spleen. </li></ul><ul><li>Platelet surface membrane has Phospho lipids, Cholesterol & glycolipids </li></ul>NOMAD:2006:BP:Thrombocytes
  10. 10. THROMBOCYTES: FUNCTIONS <ul><li>Formation of Platelet plugs in Hemostasis. </li></ul><ul><ul><li>Activation. </li></ul></ul><ul><ul><li>Adhesion. </li></ul></ul><ul><ul><li>Aggregation/ Accumulation. </li></ul></ul><ul><ul><li>Cohesion or Plug formation </li></ul></ul><ul><li>Supporting Coagulatory mechanisms. </li></ul><ul><li>Phagocytosis. </li></ul><ul><li>Storage & transport of substances. </li></ul>NOMAD:2006:BP:Thrombocytes
  11. 11. <ul><li>It can by itself stop blood loss, if the tear is small. </li></ul><ul><li>Many such minute ruptures occur thousands of times every day in minute blood vessels. </li></ul><ul><li>Platelets manage to plug these very well, all by themselves. </li></ul>NOMAD:2006:BP:Thrombocytes PLATELET PLUG FORMATION
  12. 12. APPLIED ASPECTS <ul><li>Thrombocytopenia: </li></ul><ul><ul><li>Decrease in Thrombocyte count.(Normal: 1.5 – 4 Lakhs/cu.mm of blood) </li></ul></ul><ul><ul><li>Critical Thrombocyte Count is 40,000/cu.mm. </li></ul></ul><ul><ul><li>Causes Purpura: </li></ul></ul><ul><ul><ul><li>Multiple subcutaneous purplish blotches. </li></ul></ul></ul>NOMAD:2006:BP:Thrombocytes
  13. 13. IDIOPATHIC THROMBOCYTOPENIC PURPURA <ul><ul><li>Usually cause not known. </li></ul></ul><ul><ul><li>Called as Idiopathic Thrombocytopenic Purpura. </li></ul></ul><ul><ul><li>Diagnosis by: </li></ul></ul><ul><ul><ul><li>Easy bruisability & Purpura. </li></ul></ul></ul><ul><ul><ul><li>Critical Platelet count. </li></ul></ul></ul><ul><ul><ul><li>Prolonged Bleeding Time. </li></ul></ul></ul><ul><ul><li>Can be treated by giving multiple transfusions of: </li></ul></ul><ul><ul><ul><li>Whole blood </li></ul></ul></ul><ul><ul><ul><li>Platelet rich plasma: PRP </li></ul></ul></ul>NOMAD:2006:BP:Thrombocytes
  14. 14. APPLIED ASPECTS (Contd.) <ul><li>With normal thrombocyte count, purpura may occur in </li></ul><ul><li>Thrombesthenic Purpura , where the thrombesthenin is defective. </li></ul><ul><li>Thrombocytosis can cause increased predisposition for Thrombotic events. </li></ul>NOMAD:2006:BP:Thrombocytes
  15. 15. PURPURA NOMAD:2006:BP:Thrombocytes
  16. 16. NOMAD:2006:BP:Thrombocytes THROMBOCYTES: A REVIEW <ul><li>One of the three blood cells or formed element. </li></ul><ul><li>1.5 – 4.0 Lakhs/Cu.mm </li></ul><ul><li>2 – 4 Microns in diameter. </li></ul><ul><li>No nuclei. </li></ul><ul><li>Have proteins: </li></ul><ul><ul><li>Actin </li></ul></ul><ul><ul><li>Myosin </li></ul></ul><ul><ul><li>Thrombesthenin </li></ul></ul><ul><li>Have granules secreting: </li></ul><ul><ul><li>Serotonin, ADP </li></ul></ul><ul><ul><li>FSF & PDGF </li></ul></ul><ul><li>Main function: Platelet Plug formation: </li></ul><ul><ul><li>Activation </li></ul></ul><ul><ul><li>Adhesion </li></ul></ul><ul><ul><li>Aggregation </li></ul></ul><ul><ul><li>Cohesion. </li></ul></ul><ul><li>Applied Aspects: ITP </li></ul>
  17. 17. NOMAD:2006:BP:Thrombocytes THANK YOU ALL FOR LISTENING!

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