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30 Cards in this Set
- Front
- Back
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what do myeloid tissues produce?
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- bone marrow and cells:
- erythrocytes - platelets - granulocytes - monocytes |
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what do lymphoid tissues produce?
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- thymus
- lymph nodes - spleen |
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when do blood cells first appear?
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- 3rd week of fetal development from the yolk sac
- restricted to production of myeloid cells |
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where is the chief site of RBC production in the fetus?
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- the liver
- cells from the AGM (aorta/gonad/mesonephros) region migrate there in the 3rd month |
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what happens to stem cells in the 4th month of fetal development?
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- migrate to the BM for hematopoiesis
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what triggers erythropoietin release?
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- reduced oxygenation of renal juxtaglomerular cells -> increase in production of EPO -> stimulates proliferation of CFU-E cells in the marrow
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define: thrombocytosis
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- increase in platelet production
- often follows blood loss |
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what is indicative intravascular hemolysis?
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- decreased serum haptoglobin
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what happens when haptoglobin is depleted?
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- free Hb is prone to oxidation to methemoglobin (brown)
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when does extravascular hemolysis take place?
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- when RBCs are rendered 'foreign' or become less deformable
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what do you see in intravascular hemolysis that you don't see in extravascular hemolysis?
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- you don't get hemoglobinemia and hemoglobinuria in extravacular hemolysis
- you do get 'work' hyperplasia of the spleen (splenomegaly) in extravascular hemolysis |
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why do you get a sphere shape in heereditary spherocytosis?
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- reduced membrane stability leads to loss of membrane fragments during exposure to sheer stress in the circulation
- cell has to assume the smallest diameter for a given volume -> sphere |
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how do parvoviruses cause aplastic crises?
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- infect and kill RBC progenitors -> decreased RBC production until an effective immune response pushes back the infection (takes 1-2 weeks)
- b/c the lifespan of hereditary spherocytosis RBCs is so short (10-20 days), even a brief cessation in erythropoises causes a sudden worsening in anemia |
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what does G6PD do?
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- rexuces NADP to NADPH
- oxidizes glucose-6-phosphate |
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which infections can cause oxidative damage in G6PD deficiency?
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- viral hepatitis
- pneumonia - typhoid fever |
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what are Heinz bodies?
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- membrane bound precipitates
- seen when G6PD defiiency cells are exposed to oxidants -> oxidation of reactive sulfhydryl groups on globin chains -> become denatured and form membrane bound precipitates |
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what are bite cells?
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- seen in G6PD deficiency
- Heinz bodies damage RBC bodies - when RBCs pass through splenic cords, macrophages pluck out the Heinz bodies -> look like bites were taken out! |
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what is the Hb constitution in a normal person?
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- mainly HbA (a2b2)
- some HbA2 (a2d2) - some fetal Hb (a2g2) |
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why don't heterozygous individuals for HbS normally sickle?
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- the relatively low concnetration of HbS (40%) and the interfering HbA prevent efficient HbS aggregation and polymerization
- these individuals have the sickle trait |
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why don't newborns get sickle cell anemia until 5-6 months of age?
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- HbF inhibits the polymerization of HbS
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what are the two types of megaloblastic anemias? what is the final outcome?
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1) pernicious anemia
2) folate deficiency anemia - final outcome: impaired DNA synthesis |
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what do vit B12 and folic acid have in common?
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- are cofactors for synthesis of thymidine (T)
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what is anisocytosis?
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- variation in the size and shape of red cells
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what is another name for vitB12?
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- cobalmin, a complex organometallic ompound
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what secretes intrinsic factor?
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- parietal cells of the fundic mucosa
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why do you get pernicious anemia with achlorhydria?
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- vit B12 must be released from binding proteins in food by the action of pepsin in the stomach, or low pH
- particularly a problem in older people |
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what is the principle form of folic acid in plasma?
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- N5-methyl FH4
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what is methylcobalamin?
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- an essentail cofactor for methionine synthase, the enzyme needed for converting homocysteine to methionine
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what does FH4 do?
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- converts dUMP to dTMP for DNA synthesis
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what fundamentally accounts for the impaired DNA synthesis in vit B12 deficiency?
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- reduced availability of FH4, b/c it's trapped as N5-methyl FH4
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