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  1. Describe the normal RBC membrane structure (w/ percentages)
    • Lipids: ~42%
    • phospholipids
    • glycolipids and cholesterol
    • Proteins: ~50%
    • integral (penetrating) proteins
    • peripheral structural proteins
    • spectrin helps to maintain shape
    • Carbohydrate: ~8%
  2. What are the functions of the RBC membrane?
    • Maintain shape
    • Control volume and water content
    • estimated ~300 Na/K pump per cell
    • Protects against foreign invaders
  3. Describe erythrocyte metabolism IN DETAIL
    • Embden-Meyerhof pathway: critical to producing ATP for Na/K pump
    • generates NADH for methemoglobin reductase
    • Methemoglobin reductase pathway: reduces methemoglobin
    • Leubering-Rapaport shunt: 2,3-DGP regulates O2 loading/unloading of hgb
    • Hexose monophosphate shunt (phosphogluconate): G-6-PD prevents oxidation (prevent methemoglobin formation)
    • NADPH created during pathway
  4. What is unique about the spleen compared to other lymph tissue?
    • Largest accumulation of lymphoid tissue in the body
    • Only lymphoid tissue with blood circulating through it
  5. Describe the spleen anatomy and blood flow
    • White pulp: contains lymphocytes
    • Red pulp: contains RBC, WBC, platelets, fixed and free macrophages
    • Slow blood flow from arteries to sinuses (lined by M0) and lastly to veins
  6. Describe how RBCs interact with the spleen
    • Go to spleen ~120 times per day
    • RBC must squeeze between cords of cells to enter, then return to normal shape
    • 30 sec/journey for normal RBCs
    • Abnormal cells stay minutes to hours
    • Environment is stagnant, acidic, hypoxic, and hypoglycemic
  7. What are the functions of the spleen w/ description?
    • Hematopoetic: some RBC creation
    • Culling: being discressionary about keeping RBCs
    • Pitting: removes internals of diffusely basophilic erythrocytes (reticulocytes) to become RBC
    • immunologic: removal of parasites from RBC
    • reservoir: 20-30mL blood, 30% platelets
    • *splenomegaly may result in 80-90% platelets
  8. What are the consequences of splenectomy
    • Slight increase in diffusely basophilic erythrocytes (reticulocytes) in the blood
    • Inclusions increase (Howell-Jolly bodies, other inclusions
    • Abnormal RBC morphology increases (target cells, burr cells)
    • High platelet count with large, abnormal platelets
    • WBC increase
  9. Describe the changes that occur as RBCs age (senescence)
    • Increases
    • membrane-bound IgG (added in spleen)
    • density (loss of membrane)
    • spheroidal shape
    • MCHC¬†
    • Internal viscosity
    • Agglutinability
    • Na+ (loss of Na/K pump)
    • Methemoglobin (issues with O2 affinity)
    • O2 affinity
    • Decreases
    • Enzyme activity
    • Deformability
    • MCV
    • phospholipid
    • cholesterol
    • K (loss of Na/K pump)
    • Protoporphyrin
  10. Where does erythrocyte destruction typically occur?
    • 90% extravascular
    • 10% intravascular
  11. Describe extravascular erythrocyte destruction
    • RBC: breaks into heme and globin
    • Heme: is further broken down into Fe and protoporphyrin
    • Protoporphyrin: is broken into CO and unconjugated bilirubin
    • Unconjugated bilirubin: is conjugated with glucuronic acid in the liver
    • Biliruben (most): is converted to urobilinogen and urobilin by bacteria in the large intestine
    • Biliruben and urobilinogen: recirculated to liver
    • Biliruben and urobilinogen: transfered to kidney via enterohepatic circulation and excreted in urine
  12. Describe intravascular erythrocyte destruction
    • RBC: breaks into (oxidized) Hgb tetramer¬†
    • Hgb tetramer: breaks into Hgb dimer and methemoglobin
    • Hgb dimer: goes to kidney and is released as hemosiderin, hemoglobin, and methemoglobin
    • some is transferred to liver via haptoglobin carrier protein
    • Methemoglobin: breaks into globin and heme
    • Heme: transferred to live via methemalbumin and hemopexin carrier proteins
    • heme and hgb dimer (in the liver) broken down into Fe and conjugated bilirubin by hepatocytes
    • released as urobilinogen in feces
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