Hematopoiesis & Erythropoiesis

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Myelopoiesis

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Granulocytes: neutrophils, eosinophils, and basophils

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Monopoiesis

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The mononuclear-phagocyte system (MPS)

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Hematopoietic Development: Mesoblastic phase

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In fetus: A few weeks to 2 months = yolk sac (Primitive hematopoiesis)

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Hematopoietic Development: Hepatic phase

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In fetus: 2 to 7 months = Liver (Definitive hematopoiesis)

3 to 6 months = Spleen, kidney, thymus, and lymph nodes

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Hematopoietic Development: Medullary phase

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In fetus: 7 months to birth = Bone marrow

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Hematopoietic Development: Birth

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Entire medullary space

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Hematopoietic Development: Birth-4 years

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Decrease production in long bones. Fat cells production

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Hematopoietic Development: Adults 18-20 years

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Sternum, ribs, pelvis, vertebrae, skull

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Glycophorin

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Integral membrane protein. Carries most of sialic acid, which is responsible for the negative charges of the RBCs, membrane receptors, and RBC antigens

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Peripheral membrane proteins

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Line inner membrane surface to form membrane skeleton. Strengthen the membrane and controls biconcave shape.

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Hypoxia

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Decrease of O2 in tissues

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Hypoxemia

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Decrease of O2 in blood, arterial pO2 < 80 mm Hg

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Cyanosis

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Increase of deoxyhemoglobin in blood; leads to blue discoloration of skin

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Glycosylated hemoglobin

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Hgb A1, glucose is irreversibly attached, indicator for blood glucose level

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Intravascular hemolysis

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10% of normal RBC destruction with 3 iron salvage systems: haptoglobin, hemopexin, and methemalbumin

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Vitamin B12

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AKA cobalamin. Only vitamin exclusively synthesized by microorganisms. Low daily requirement and high storage rate (primarily in liver). Manifest deficiency in years.

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Folic acid

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H2O soluble vitamin. Heat labile, thus easily destroyed by cooking. High rate of absorption and turnover time, but high rate of loss. Manifest deficiency in months

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Liver

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Extra-medullary hematopoiesis. Hemostasis, protein synthesis/transport, RBC sequestration (conjugation of bilirubin), storage, kupffer cells

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Spleen

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Extra-medullary hematopoiesis. Located under left side of rib cage. We can live w/o spleen, but weaker immune system.

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Thymus

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Extra-medullary hematopoiesis. First developed organ in fetus and major site of T-cell production.

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Lymph nodes

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Bean-shaped. Functions include lymphopoiesis and Ig production

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Kidney

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Under hypoxic conditions, the kidney will produce and secrete erythropoietin (EPO) to increase the production of red blood cells

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Rubriblastic nomenclature

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Rubriblast, prorubricyte, rubricyte, metarubricyte, reticulocyte, erythrocyte

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Normoblastic nomenclaure

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Pronormoblast, basophilic normoblast, polychromatic normoblast, orthochromic normoblast, reticulocte, and erythrocyte

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Erythroblastic nomenclature

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Erythroblast, basophilic erythroblast, polychromatic erythroblast, orthochromic erythroblast, reticulocyte, erythrocyte

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Reticulocyte

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Polychromatic erythrocyte

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Embden-Meyerhof Pathway

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Anaerobic glycolysis. 90% ATP (2 consumed, 4 generated). Begins with glucose, ends with pyruvate then lactate

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Hexose Monophosphate Pathway

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AKA pentose phosphate shunt. Aerobic glycolysis. 10% ATP. Oxidative phase generates NADPH using G6P, which helps prevent oxidative stress by converting H2O2 to H2O.

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Methemoglobin Reductase Pathway

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Glyceraldehyde converts NAD to NADH in glycolysis, then NADH converts back to NAD w/ rxn from methemoglobin reductase. Methemoglobin is then converted to hemoglobin (prevents oxidation of heme).

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Methemoglobin

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A form of hemoglobin in which the iron component has been oxidized from the ferrous to ferric state. Methemoglobin cannot carry oxygen.

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Rapoport-Luebering Pathway

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When O2 supply is reduced, there is an increase in deoxyhemoglobin, which leads to increased binding of DPG and helps increase glycolysis

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Embryonic hemoglobins

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Primitive hemoglobins formed by immature erythrocytes in yolk sac that include Gower I and II and Portland types. Zeta chain is analogous to alpha chain of fetal/adult hgb and epsilon chain is analogous to gamma, beta, and delta chains.

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Fetal hemoglobins

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Hemoglobin F has two alpha and two gamma chains. This hgb type is associated with hepatic erythropoiesis. At about 6 months of age, adult hemoglobin predominates. Also has increased affinity for oxygen.

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Oxygen dissociation curve (right shift)

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Increase in: O2 release to tissues, 2,3 DPG, and body temp.
Decrease in: pH (acidosis) and O2 affinity
Associated with anemia

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Oxygen dissociation curve (left shift)

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Increase in: pH (alkalosis) and O2 affinity
Decrease in: O2 release to tissues, 2,3 DPG, and body temp.
Associated with: Multiple transfusion

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2,3-DPG

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Combines with beta chains of deoxyhemoglobin and diminishes molecule's affinity for oxygen

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Hemoglobin F

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Fetal Hgb, 2 alpha 2 gamma, primarily in cord blood, high O2 affinity, does not bind to 2,3 DPG, higher volume of blood in fetus

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Methemoglobin

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Abbreviated as Hi, binds to Ferric ions, incapable of binding to O2, in high concentration causes hypoxia and cyanosis, increase by oxidizing chemicals/drugs, deficiency of metHg reductase (genetic), treatment is ascorbic acid or methylene blue

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Sulfhemoglobin

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Caused by drugs/chemicals, irreversible binding to sulfur-containing chemicals, persists for life

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Carboxyhemoglobin

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Heme iron binds to carbon monoxide, 200x more affinity for CO than for O2 w/ much slower release of CO than O2, derived from exhaust or industrial pollutants

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Ferritin

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Primary iron storage in liver, spleen, and bone marrow. Easily immobilized by the body for utilization

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Hemosiderin

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Primary iron storage in bone marrow. Composed of insoluble aggregates of ferritin, proteins, and some lipids. Less readily available for utilization and is released more slowly

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Extravascular hemolysis

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Erythrocyte is phagocytized and digested by macrophages and the hemoglobin is disassembled into iron, protoporphyrin, and globin. Iron is transported to plasma by transferrin to be recycled in marrow, globin is catabolized in liver into AA and recycled, and porphyrin ring (heme) is either exhaled as CO2 or transported by plasma albumin into the liver and broken down into unconjugated bilirubin, which is eventually discarded in urine as urobilinogen or in feces as stercobilinogen.

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Haptoglobin

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RBC destruction results in hgb being released directly into bloodstream and undergoes dissociation into alpha and beta dimers, which are quickly bound to plasma haptoglobin. This stable complex prevents urinary excretion. It is removed from circulation by hepatocytes and broken down into its components. Once plasma haptoglobin is depleted, unbound hgb alpha and beta dimers are filtered by glomeruli in kidneys, reabsorbed, and either converted hemosiderin where it is excreted or remains in epithelial cells.

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Hemopexin

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Hemoglobin that is neither bound by haptoglobin nor directly excreted is oxidized to methemoglobin. The heme groups are released and taken up by hemopexin, which is a plasma protein that binds heme with high affinity. The complex is then processed in the liver.

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Methemalbumin

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Heme groups from methemoglobin combine with albumin to form methemalbumin until more hemopexin is available.

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Methionine

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Vitamin B12 (as Me-Cbl) and folic acid (as MTHF) help convert homocysteine to methionine through methylation in the cytoplasm.

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Methylmalonic acid

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Requires B12 as a cofactor (adenosyl-Cbl) to form succinyl CoA in mitochondria for Hgb synthesis or fatty acid oxidation.