Hematology Ch.5

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Hematology Ch.5
2013-02-09 22:58:35
RBC life cycle

Life cycle
Show Answers:

  1. Characteristics of RBCs:
    • Uniform
    • Flattened
    • Biconcave disks
  2. Erythropoiesis:
    RBC production
  3. Hemoglobin synthesis requires 3 basic components:
    • Amino acids
    • Iron
    • Vitamins B12 and B6 and Folic Acid
  4. Functions of RBCs:
    • Transports oxygen from lungs to tissues.
    • Transports CO2 from tissues to the lungs.
  5. Erythropoietin:
    Glycoprotein hormone (growth factor) that stimulates erythropoiesis.
  6. Where does erythropoietin happen?
    85% in kidneys, 15% in liver
  7. Erythropoietin synthesis is stimulated by and located on chromosome:
    hypoxia, 7
  8. Decreased blood oxygen (hypoxia) is detected by special kidney cells, which:
    Stimulates them to produce erythropoietin
  9. Erythropoietin is secreted into the:
    blood and travels to the bone marrow
  10. Can RBCs counts get too high?
    Yes, blood becomes so thick, heart can not pump leads to clot/blood vessel.
  11. Polycythemia:
    Increased RBC concentration
  12. Absolute Polycythemia:
    • Secondary.
    • Increased numbers of RBCs (High erythropoietin, smokers, chronic lung disease, abnormal hemoglobin molecules, renal tumors, genetic disorders)
  13. Relative polycythemia:
    • Primary.
    • Decreased plasma volume (Not related to high erythropoietin, RBC numbers are not increased, Dehydration from burns, diarrhea, decreased fluid intake or exposure to excessive heat)
  14. Developement and maturation of RBCs:
    • Rubriblast (Pronormoblast): Fine chromatin, 0-2 nucleoli, basophilic cytoplasma, receives iron from hemoglobin.
    • Prorubricyte (Basophilic normoblast):Thicker chromatin, no nucleoli
    • Rubricyte (Polychromatic normoblast): Coarse chromatin, "muddy grey" cytoplasm 1st visible hemoglobin
    • Metarubricyte (Orthochromatic normoblast): Pyknotic nucleus (dark solid), pinkish cytoplasm
    • Reticulocyte: Anuclear RBC with bluish tint
    • Erythrocyte (Mature RBC): Anuclear, pink-red cytoplasm
  15. Megaloblastic maturation
    • Delayed nuclear maturation but normal cytoplasm maturation.
    • Immature nucleus and mature cytoplasm.
    • The nucleus and cytoplasm are asynchronous
    • Common cause of megaloblastic maturation is B12 deficiency.
  16. Reticulocyte (retic):
    • RBC after nucleus is lost.
    • Briefly retains RNA, causing bluish discolorization (Wright stain)
  17. When is the RNA lost in a reticulocyte?
    1-2 days after release
  18. Under normal conditions in retic:
    • Bone marrow retics replace old RBCs removed from circulation.
    • # marrow RBCs=# Blood retics=#RBCs removed from blood
  19. Stress retics:
    • Reticulocytes released earlier than normal to meet increased demand.
    •     Immature, larger than normal and have a
    •     darker bluish color.
  20. Retic count:
    • Common test to measure bone marrow erythropoiesis.
    • RNA will stain a smooth light blue color with the Wright Stain.
    • RNA is precipitated and stains as bluish granules (speckled appearance) with Methylene Blue stain.
  21. Retics are expressed as a _____.
    % of total RBCs
  22. Retic counts are performed in 2 ways:
    • Microscopic exam of Methylene blue stained blood smear.
    • Automated analysis of Methylene blue stained whole blood
  23. What is the corrected retic formula?
    (patient HCT/Normal HCT) retic %
  24. Uncorrected Retic formula:
    #retics/#RBCs x 100
  25. (RPI) Reticulocyte Production Index:
    Corrected Retic count/Maturation time
  26. RPI is done to correct:
    For apparent increase in erythropoiesis
  27. Hemoglobin is a large, coiled, conjugated protein molecule that is composed of:
    • 4 polypeptide chains composed of amino acids.
    • 4 heme groups
    • 4 iron molecules, 1 in each heme group
  28. Adult hemoglobin:
    2 alpha-2 beta chains
  29. 2-3 DPG:
    • Molecule found inside the RBCs
    • 2-3 DPG is high the oxygen will leave the RBC cell to the other cells (good).
    • If low it will soak up the oxygen.
  30. Increased 2-3 DPG _________ affinity:
  31. Increased PO2 _______ affinity.
  32. Increased temp _________ affinity.
  33. Increase pH __________ affinity
  34. Increase O2 affinity:
    Shift to Left
  35. Decreased O2 affinity:
    Shift to right
  36. Fetal hemoglobin has _______ O2 affinity than HGB A. Pulls O2 across placenta from mother to fetus.
  37. Hemoglobin F:
    • 2 Alpha-2 gamma
    • Synthesis begins at 5 weeks gestation and associated with hepatic hematopoiesis
  38. Carbon Dioxide Transport. Hemoglobin is also needed to transport carbon dioxide from the tissues back to _______ for removal.
  39. Carbon dioxide transported 3 different ways:
    _____ Indirect RBC pathway (conversion of CO2 to HCO3)
    ____ Direct pathway
    ____ Dissolved in plasma
    75%, 20%, 5%
  40. Porphyrias:
    Disorder of heme synthesis
  41. Causes of porphyrias:
    • Genetic deficiencies of enzymes required for heme synthesis.
    • Acquired deficiencies from substances that damage heme synthesis.
  42. Porphyrias are diagnosed:
    From detection of heme pre-cursors molecules in the urine
  43. Ferric iron is transported to the immature marrow RBCs by the protein ______.
  44. Transferrin delivers ____ to the immature RBC membrane and then returns to the plasma.
  45. Excess iron is stored as ________ in tissues and plasma.
  46. Ringed sideroblasts
    Excess iron may accumulate in immature RBCs
  47. Hemoglobin A2:
    2 alpha-2 delta
  48. Barts:
    4 Gamma
  49. Hemoglobin S:
    2 alpha-2 beta (6 Glucose--Valence
  50. Hemoglobin C:
    2 alpha-2 beta (6 glucose-lysine)
  51. Carbon monoxide:
    • Hemoglobin affinity for CO >200 x that of oxygen.
    • Hgb binds CO and releases it very slowly.
  52. Can carboxyhemoglobin transport oxygen?
  53. Sulfhemoglobin:
    • Hemoglobin combined with sulfur compounds.
    • Hemoglobin shape altered, preventing oxygen transport.
    • May denature and precipitate to form Heinz Bodies.
  54. Common causes of sulfhemoglobin:
    • Drugs
    • Bacterial infections
  55. Methemoglobin:
    • Hemoglobin with ferric iron.
    • Caused by genetic defects/oxidizing drugs
  56. Hemoglobin electrophoresis:
    • Analytical technique that separates substances according to their different migration rates (movement) in an electric field.
    • Commonly used to confirm a hemoglobinopathy diagnosis.
  57. What are the 2 most common hemoglobin electrophoresis technique:
    • Cellulose acetate
    • Citrate agar
  58. Cellulose acetate has a pH of:
  59. Citrate agar has a pH of:
    < 7.0
  60. Fetal Hemoglobin stain or Hemoglobin F stain is also known as:
    • Kleihauer-Betke Stain
    • useful to ID fetal blood in the maternal circulation
  61. Embden-Meyerhof Pathway:
    Main energy source/ATP from glucose
  62. Hexose Monophosphate Shunt:
    Prevents oxidative denaturation of hemoglobin and Heinz Body formation
  63. Methehemoglobin reducatase pathway:
    prevent oxidation of hemoglobin iron to Fe3+
  64. Luebering-Rappaport Pathway:
    Regulates 2-3 DPG concentration in the RBCs
  65. What is the average lifespan of RBCs?
    4 months
  66. As RBCs age what happens:
    • Membrane become less flexible
    • Enzyme activity decreases.
    • Cell loses membrane-RBC hemoglobin increases
  67. Cup of grace Coup de grace:
    • As RBC's become stiff, they get stuck passing through the spleen.
    • Phagocytized and removed from the circulation by the spleen.
    • RBCs are destroyed.
    • The components of the RBCs must be re-utilized or excreted.
  68. Extravascular catabolism (Intracelluar):
    • Happens in spleen. Inside the RE cells of spleen.
    • Heme is broken apart and concerted into bilirubin and excreted into the GI tract by the liver.
  69. Intravascular catabolism (in the circulating blood):
    RBCs hemolyze, releasing the cytoplasm into the plasma.
  70. Haptoglobulin:
    • Plasma protein binds polypeptide chains, preventing their loss in the urine.
    • Haptoglobin-protein complexes removed by the liver.
    • Additional unbound plasma hemoglobin oxidized to methemoglobin.
  71. MCV (fL):
    • Mean Corpuscular volume
    • How big, average
  72. MCH (pg):
    • Mean Corpuscular Hemoglobin
    • How much hemoglobin in cell.
  73. MCHC (g/dl):
    • Mean Corpuscular Hemoglobin Concentration
    • Concentration of hemoglobin
  74. Formula for MCV:
    HCT/RBC (10)
  75. Formula for MCH:
    HGB/ RBC (10)
  76. Formula for MCHC:
    HGB/HCT (100)