PLATELET (Thrombocyte) - Short notes


  • SIZE : 2 - 4 micro meter in diameter 
  • COLORcolorless
  • SHAPE: oval,disc shaped 
  • Platelets are seen using specialized stain such as leishmans stain ,on staining it appears bluish ,granular cytoplasm
  • There is  NO NUCLEUS present in platelet and hence cannot be reproduced .
  • Blood is a specialized body fluid .
  • Blood products : white blood cells ,red blood cells ,plasma ,platelet.
  • WHITE BLOOD CELLS :colorless ,nucleated cell,plays an important role in defense mechanism of body.
  • white blood cell include : neutrophil,eosinophil,basophil,lymphocyte and monocyte .
  • normal white blood cell count : 4,000 to 11,000 cells per milli meter cube .
  • RED BLOOD CELLS:  Red blood cell develop from erythrocyte ,derived from progenitor cells.
  • Normal hemoglobin level in blood : 
  1.  Adult male - 15 to 18 gram per deci litre 
  2. Adult female - 11.5-13 gram per deci litre
  3.  Newborn - 15 gram per deci litre
  4.  3 month old : 9 gram per deci litre.
  • PLASMA:  clear ,straw colored fluid with dissolved solid substances.
  • plasma constitutes 55% of blood.

  • platelets when observed on an electron microscope :
  • cell membrane : 
  1. Glycoprotein : This coats the plasma membrane prevent adhesion to endothelial cell ,accelerate adhesion to collagen at injured blood vessel.
  2. Phosphoipid : it plays an important role in blood coagulation 
  3. Invaginatin :canaliculai system 
  4. Receptor : bind to specific fibronogen and collagen
  5. Precursor; prostaglandin present.
  • MICRO TUBULE : compact bundle found beneath plasma membrane ,help in maintaining platelet shape.
  • CYTOPLASM: cytoplasm consist of contractile protein like actin,myosin,platelet derived growth factor and von willebrand factor.

  1. ADHESION:  platelet adhesion is activated when met with wet able or rough surface ,due to presence of thrombaxone A2,thrombin, von willebrand factor.
  2. AGGREGATION: pile of platelet during clot formation due to presence of adinosine diphosphate and thrombaxone A2 .
  3. AGGLUTINATION: clumping of platelet due to platelet agglutinin.

  1. HEAMOSTASIS : spontaneous arrest of bleeding from injured blood vessel, for more information refer -  heamostasis
  2. clot formation: it helps in formation of intrinsic prothrombin.
  3. Role in clot retraction
  4. Repair of injured blood vessel
  5. Defense mechanism
  6. Storage and transport : 5 HT produced is transported to injured blood vessel

  • APPLIED ASPECT :  Normal platelet count : 1,50,000 per milli meter cube -4,50,000 milli meter cube.

  1. THROMBOCYTOSIS: Increase in platelet count above 4.5 lakhs per milli meter cube.
  2. THROMBOCYTOPENIA: Decrease in platelet count below 1.5 lakhs per milli meter cube.

DO  let me know in comment section if you  want me to post notes for each blood products .

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