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30 Cards in this Set

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what do myeloid tissues produce?
- bone marrow and cells:
- erythrocytes
- platelets
- granulocytes
- monocytes
what do lymphoid tissues produce?
- thymus
- lymph nodes
- spleen
when do blood cells first appear?
- 3rd week of fetal development from the yolk sac
- restricted to production of myeloid cells
where is the chief site of RBC production in the fetus?
- the liver
- cells from the AGM (aorta/gonad/mesonephros) region migrate there in the 3rd month
what happens to stem cells in the 4th month of fetal development?
- migrate to the BM for hematopoiesis
what triggers erythropoietin release?
- reduced oxygenation of renal juxtaglomerular cells -> increase in production of EPO -> stimulates proliferation of CFU-E cells in the marrow
define: thrombocytosis
- increase in platelet production
- often follows blood loss
what is indicative intravascular hemolysis?
- decreased serum haptoglobin
what happens when haptoglobin is depleted?
- free Hb is prone to oxidation to methemoglobin (brown)
when does extravascular hemolysis take place?
- when RBCs are rendered 'foreign' or become less deformable
what do you see in intravascular hemolysis that you don't see in extravascular hemolysis?
- you don't get hemoglobinemia and hemoglobinuria in extravacular hemolysis
- you do get 'work' hyperplasia of the spleen (splenomegaly) in extravascular hemolysis
why do you get a sphere shape in heereditary spherocytosis?
- 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
how do parvoviruses cause aplastic crises?
- 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
what does G6PD do?
- rexuces NADP to NADPH
- oxidizes glucose-6-phosphate
which infections can cause oxidative damage in G6PD deficiency?
- viral hepatitis
- pneumonia
- typhoid fever
what are Heinz bodies?
- 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
what are bite cells?
- 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!
what is the Hb constitution in a normal person?
- mainly HbA (a2b2)
- some HbA2 (a2d2)
- some fetal Hb (a2g2)
why don't heterozygous individuals for HbS normally sickle?
- the relatively low concnetration of HbS (40%) and the interfering HbA prevent efficient HbS aggregation and polymerization
- these individuals have the sickle trait
why don't newborns get sickle cell anemia until 5-6 months of age?
- HbF inhibits the polymerization of HbS
what are the two types of megaloblastic anemias? what is the final outcome?
1) pernicious anemia
2) folate deficiency anemia
- final outcome: impaired DNA synthesis
what do vit B12 and folic acid have in common?
- are cofactors for synthesis of thymidine (T)
what is anisocytosis?
- variation in the size and shape of red cells
what is another name for vitB12?
- cobalmin, a complex organometallic ompound
what secretes intrinsic factor?
- parietal cells of the fundic mucosa
why do you get pernicious anemia with achlorhydria?
- 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
what is the principle form of folic acid in plasma?
- N5-methyl FH4
what is methylcobalamin?
- an essentail cofactor for methionine synthase, the enzyme needed for converting homocysteine to methionine
what does FH4 do?
- converts dUMP to dTMP for DNA synthesis
what fundamentally accounts for the impaired DNA synthesis in vit B12 deficiency?
- reduced availability of FH4, b/c it's trapped as N5-methyl FH4