Introduction to Platelets
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Questions and Answers

What triggers primary hemostasis upon blood vessel injury?

  • Nucleated blood components
  • Platelets
  • Endothelial cell inflammatory proteins (correct)
  • Subendothelial cholesterol

    • What is the normal range of platelets in women?

  • 120-350x10^9/L
  • 100-300x10^9/L
  • 250-500x10^9/L (correct)
  • 150-400x10^9/L

    • What factor recruits megakaryocyte progenitors from common myeloid progenitors?

  • Thrombopoietin (TPO) (correct)
  • Leukopoietin
  • Erythropoietin
  • Monocytopoietin

    • Which cells act to balance megakaryocytopoiesis and erythropoiesis through their opposing actions?

    <p>GATA-1 and MYB</p> Signup and view all the answers

    What is the role of megakaryocytes in the bone marrow?

    <p>Produce platelets</p> Signup and view all the answers

    In what type of patients are platelets slightly lower?

    <p>Those over 65 years old</p> Signup and view all the answers

    Which progenitor stage is the most immature in the megakaryocyte lineage?

    <p>BFU-Meg</p> Signup and view all the answers

    What characterizes the progenitor stage of CFU-Meg Diploids?

    <p>Undergoes endomitosis</p> Signup and view all the answers

    Which transcription factors are associated with endomitosis in the megakaryocyte lineage?

    <p>RUNX1 and NF-E2</p> Signup and view all the answers

    What is a key feature of the terminal differentiation of a Promegakaryocyte into a Megakaryocyte (MK-I)?

    <p>Formation of proplatelet processes</p> Signup and view all the answers

    Where do Megakaryocytes release platelets from during terminal differentiation?

    <p>Proplatelet processes into circulation</p> Signup and view all the answers

    What is the alternative name for the Eicosanoid synthesis pathway?

    <p>Prostaglandin pathway</p> Signup and view all the answers

    Which enzyme converts arachidonic acid to prostaglandin G2 and prostaglandin H2?

    <p>Cyclooxygenase</p> Signup and view all the answers

    What effect does TXA2 have on adenylate cyclase activity?

    <p>Decelerates it</p> Signup and view all the answers

    What is the function of Prostacyclin in endothelial cells?

    <p>Raises cyclic CAMP levels</p> Signup and view all the answers

    Which pathway is triggered by G-proteins and involves phospholipase C activation?

    <p>IP3-DAG activation pathway</p> Signup and view all the answers

    What binds guanosine diphosphate (GDP) when G-proteins are inactive?

    <p>Cyclooxygenase</p> Signup and view all the answers

    What is the approximate size of a mature megakaryocyte (MK-III)?

    <p>20-90 um</p> Signup and view all the answers

    Which transcription gene product suppresses megakaryocyte differentiation?

    <p>MYB</p> Signup and view all the answers

    What is the main growth factor responsible for inducing thrombocytopoiesis?

    <p>Thrombopoietin</p> Signup and view all the answers

    Where are sequestered platelets mainly found?

    <p>Spleen (white pulp)</p> Signup and view all the answers

    Which platelets compensate for thrombocytopenia and have diameters larger than ordinary mature platelets?

    <p>Reticulated platelets</p> Signup and view all the answers

    Which zone of the platelet contains glycoproteins related to the coagulation and fibrinolytic systems?

    <p>Peripheral zone</p> Signup and view all the answers

    What is the function of phospholipase C in the context described?

    <p>It cleaves membrane phosphatidylinositol 4,5-bisphosphate to form IP3 and DAG, which are second messengers for intracellular activation.</p> Signup and view all the answers

    What is the primary role of IP3 in the context described?

    <p>It promotes the release of ionic calcium from the dense tubular system (DTS), which triggers actin microfilament contraction.</p> Signup and view all the answers

    What is the function of DAG in the context described?

    <p>It triggers a multistep process involving the activation of phosphokinase C, which triggers phosphorylation of the protein pleckstrin, which regulates actin microfilament contraction.</p> Signup and view all the answers

    What is the purpose of using EDTA in the platelet counting procedure described?

    <p>To prevent clotting of the blood sample during the counting process.</p> Signup and view all the answers

    What is the purpose of using a phase-contrast microscope in the platelet counting procedure described?

    <p>To visualize and count the platelets in the sample.</p> Signup and view all the answers

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