II. Physiology: Erythropoietin

  1. Primary Hormone regulator of RBC production
  2. Erythropoietin sources
    1. Fetus: Monocyte and Macrophage system in liver
    2. Postnatal: Peritubular cells in Kidney

III. Physiology: Red Blood Cell

  1. Hemoglobin produced until amounts to 90% of RBC mass
  2. Red Blood Cells start as Reticulocytes in Bone Marrow
    1. Reticulocytes are juvenile Red Blood Cells
      1. Nucleus extruded once RBC has matured
      2. Reticulocytes contain ribosome remnants
        1. Immature Reticulocytes contain most ribosomes
        2. Mature Reticulocytes contain least ribosomes
    2. Reticulocytes have 4 day life span
      1. Bone Marrow: 3 days (less if Erythropoietin high)
      2. Peripheral blood: 1 day
  3. Red Blood Cell survival
    1. Normal RBC: 120 days
    2. Abnormal RBC: May survive as little as 15 days
    3. Following transfusion: RBC survival 2-3 weeks

IV. Physiology: Hemoglobin

  1. Images
    1. hemoglobin.jpg
  2. Heme Protein complex
    1. Central iron-containing heme ring attached to
    2. Two pairs of polypeptides (4 total)
      1. A pair of alpha chains are found in every normal Hemoglobin type
      2. A pair of other polypetides depending on type (Gamma, Beta, Delta)
  3. Six types of normal Hemoglobin
    1. Embryonic
    2. Gower I
    3. Gower II
    4. Portland
    5. Fetal Hemoglobin (HbF): Alpha2-Gamma2
      1. Primary Hemoglobin in fetus
      2. Replaced by Adult Hemoglobin by age 6-12 months
    6. Adult Hemoglobin (HbA): Alpha2-Beta2
    7. Adult Hemoglobin (HbA2): Alpha2-Delta2
  4. Thalassemia related Hemoglobins
    1. Hemoglobin Bart's: Gamma4
      1. Seen in Alpha Thalassemia
    2. Hemoglobin H: Beta4
      1. Seen in Beta Thalassemia
  5. Hemoglobin Metabolism
    1. Hemoglobin breakdown occurs when Red Blood Cells are destroyed (e.g. in Spleen at the end of their roughly 120 day life cycle)
    2. Hemoglobin is converted into Biliverdin and ultimately into Bilirubin for excretion
    3. See Bilirubin

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