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2013-05-03 00:09:08
Intro Diseases Conditions Thrombocytes

Intro, Diseases and Conditions, Thrombocytes
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  1. Upon injury to the endothelium, what happens?
    • Increased vascular permeability occurs
    • LeakageĀ of plasma proteins and blood cell migration occurs to the site of injury
    • Damage causes vasoconstriction to minimize blood loss
    • Allows interaction among vessels, platelets, and plasma proteins
  2. What happens when the subendothelium is damaged?
    • Exposure to collagen causes platelet activation
    • Activates intrinsic pathway of secondary hemostasis
  3. What does the vascular endothelium produce or release that are important in hemostasis?
    • von Willebrand Factor (vWF)
    • Tissue factor
    • Tissue plasminogen activator
    • Prostacyclin
    • Endothelial surface receptor thrombomodulin
  4. What is the purpose of von Willebrand Factor (vWF)?
    • Necessary for platelet adhesion to collagen
    • Carrier protein for coagulation factor VII:C
  5. What is the purpose of Tissue factor?
    • Tissue factor in vessels is exposed during vessel damage
    • Activates the extrinsic pathway of secondary hemostasis
  6. What is the purpose of Tissue plasminogen factor?
    • Released during vessel damage
    • Activates the fibrinolytic system
  7. What is the purpose of prostacyclin?
    • Platelet aggregation inhibitor
    • Vasodilator
  8. What is the purpose of the endothelial surface receptor?
    Endothelial surface receptor thrombomodulin forms a complex with thrombin to inhibit factors V and VIII in secondary hemostasis through the protein C system
  9. What is the defect called when thin vessel walls cause mucous membrane bleeding?
    Hemorrhagic telangiectasia
  10. What is the defect called when abnormal collagen production causes hyperelastic skin and joint abnormalities?
    Ehlers-Danlos syndrome
  11. What happens when there is a Vitamin C deficiency?
    Scurvy - Improper collagen synthesis and vessel integrity
  12. What is Vitamin C needed for?
    Vitamin C is needed for proper collagen synthesis and vessel integrity
  13. What cell gives rise to megakaryocytes?
  14. What responds to thrombopoietin?
  15. In order, name the thrombocyte maturation cells
    • Megakaryoblast
    • Promegakaryocyte
    • Megakaryocyte
    • Thrombocytes
  16. Name the platelet zones and what they contain
    • Peripheral zone: glycoprotein receptor sites and submembrane area contains the phospholipid that serves as a surface interaction of coagulation factors to secondary hemostasis
    • Sol-gel (structural) zone: Contains microtubules, cytoskeletons, actin, and myosin
    • Organelle zone: contains granules, lysosomes, mitochondria, peroxisomes, and glycogen - which controls platelet function in response to coagulation
  17. What is included in the membrane systems and what do they do?
    • Dense tubular system (DTS): Regulator of intracellular calcium concentration
    • Open canalicular system (OCS): Releases granular contents through channels leading to the surface of the platelet
  18. What is the reference range of platelets?
    150-450 x109/L
  19. Where are platelets found?
    • 2/3 are in circulation
    • 1/3 are stored in the spleen
  20. What is the life span of platelets?
    8-12 days
  21. What do giant platelets indicate?
    • Premature release from bone marrow
    • Result from increased demand
  22. What do immature platelets indicate?
    • Acute megakaryotic leukemia
    • Myelodysplastic syndrome
  23. What are platelet function dependent upon?
    • Platelet secreted proteins: Serotonin, thromboxane A2, actomyosin
    • ATP
    • ADP
    • Calcium
    • Platelet factors: PF4, PF3
  24. What is the function of the platelet-secreted protein, serotonin?
    Serotonin stimulates vasoconstriction when vessel injury occurs
  25. What is the function of the platelet secreted protein, thromboxane A2?
    Thromboxane A2 stimulates platelet aggregation and vasoconstriction
  26. What is the function of the platelet secreted protein, actomyosin?
    Actomyosin contracts the thrombus at the end of the coagulation process
  27. What is the function of the platelet factor PF4?
    PF4 neutralizes heparin
  28. What is the function of platelet factor PF3?
    PF3 is a platelet phospholipid needed for proper platelet function and coagulation
  29. What are the steps of proper platelet function?
    • Adhesion: dependent on binding of von Willebrand factor at the GPIb
    • Release of granule contents
    • Aggregation: fibrinogen attaches at the IIb/IIIa receptor of adjoining platelets, forming the initial platelet plug, ADP, serotonin, and PF4 are released, then PF3 is released to profide the phospholipid surface needed for binding of clotting factors
    • Clot retraction: dependent on thrombasthenin and glycoprotein receptors IIb/IIIa
  30. What are some qualitative tests that analyze platelets?
    • Bleeding time
    • Platelet aggregation studies
    • vWF:Ag (antigenic) and vWF:RCo (activity) assays used to assess von Willebrand factor
  31. What condition:
    Decreased platelet adhesion causes mucous membrane bleeding that is variable in severity
    Normal platelet count
    Prolonged bleeding time
    Decreased aggregation response to ristocetin
    Variable PTT
    Normal PT
    Decreased vWF:RCo, vWF:Ag, and VIII:C
    von Willebrand disease
  32. What is the function of von Willebrand factor?
    • Needed for platelets to adhere to collagen in damaged vessels
    • Is a carrier protein for coagulation factor VIII:C
  33. What happens in von Willebrand disease?
    Decreased platelet adhesion causes mucous membrane bleeding that is variable in severity
  34. What is the most common hereditary hemorrhagic disorder and has autosomal dominant inheritance?
    von Willebrand disease
  35. What is the name of a condition where:
    Giant platelets lack glycoprotein Ib receptor
    Adhesion defect due to faulty bindingĀ of platelets to von Willebrand factor
    Variable platelet count
    Platelet anisocytosis
    Prolonged bleeding time
    Decreased aggregation response to ristocetin
    Normal PT and PTT
    Normal vWF:RCo, vWF:Ag, and VIII:C
    Bernard-Soulier syndrome
  36. What condition:
    Hemorrhagic disorder seen in populations where consanguinity is prevalent
    Lack of glycoprotein IIb/IIIa, the fibrinogen binding receptor
    Decreased aggregation response with ADP, epinephrine, and collagen
    Normal response to aggregation with ristocetin
    Glanzmann thrombasthenia
  37. What condition:
    Characterized by large platelets
    Absence of alpha granules
    Patients are prone to lifelong mild bleeding tendencies
    Gray-platelet syndrome
  38. What condition:
    Characterized by small platelets
    Decreased amount of alpha granules and dense bodies
    Patients are prone to hemorrhage and recurrent infections
    Wiskott-Aldrich syndrome
  39. What condition:
    Characterized by a lack of dense body granules
    Patients exhibit oculocutaneous albinism
    Prone to hemorrhage
    Hermansky-Pudlak syndrome
  40. What does aspirin and nonsteroidal anti-inflammatory drugs do to interfere with platelets?
    Interfere with the cyclooxygenase enzymes, preventing thromboxane A2 synthesis and subsequent aggregation
  41. What does Plavix (clopidogrel bisulfate) and ticlopidine do to interfere with platelets?
    • Both are adenosine diphosphate (ADP) receptor inhibitors
    • The blockage of this receptor inhibits platelet aggregation
  42. What does eptifibatide and similar antiplatelet meds do to interfere with platelets?
    Block IIb/IIIa glycoproteins - preventing aggregation
  43. What types of conditions can cause platelet dysfunction?
    • Myeloproliferative disorders
    • Uremia
  44. What condition:
    Uncontrolled, malignant proliferation of platelets - NOT in response to thrombopoietin
    Can be caused by essential thrombocythemia, polycythemia vera, and chronic myelocytic leukemia
    Plt count >1000 x 109/L
    Associated with either hemorrhagic or thrombotic complications
    Primary thrombocytosis
  45. What condition:
    Characterized by increased plt production usually in response to thrombopoietin
    Plt is elevated by <1000 x 109/L
    Can result from chronic and acute inflammatory disease, iron deficiency, rapid blood regeneration, exercise, prematurity, response to drugs, etc...
    Secondary (reactive) thrombocytosis
  46. What condition:
    Decrease in plts
    Can be the result of megakaryocyte hypoproliferation, ineffective thrombopoiesis, increased loss/destruction, splenic sequestration, hereditary conditions