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Exam 1 - part 4
Erythropoiesis
| Question | Answer |
|---|---|
| What does an erythropoetic progenitor cell compartment represent? | A unipotential cell committed to differentiate into erythroid cells only |
| What does a cell require to commit to becoming an erythrocyte? | Erythropoietin |
| What are the 2 progenitor cells in erythropoiesis? | BFU-E and CFU-E |
| BFU-E stands for what? | Burst forming unit - erythroid |
| What does CFU-E stand for? | Colony forming unit - erythroid |
| What progenitor cell represents the most primitive erythroid progenitor cell? | BFU-E |
| Which erythroid progenitor cell is more sensitive to erythropoietin? | CFU-E |
| What acts in synergistic action on EPO to induce proliferation and differentiation of a CFU-E? | IL-3 and GM-CSF |
| CFU-E is a precursor to what? | Pronormoblast |
| What is the first precursor cell to be morphologically distinguished as a forming RBC? | Pronormoblast |
| A RBC grows (smaller or larger) as it matures? | Smaller |
| As a RBC grows, nuclear chromatin (expands or condenses)? | Condenses as heterochromatin |
| What are the 5 stages of maturation before a RBC becomes a mature erythrocyte? | 1. Pronormoblast 2. Basophilic normoblast 3. Polychromatophilic normoblast 4. Orthochromatic normoblast 5. Polychromatophilic erythrocyte |
| Each pronormoblast gives rise to a potential of how many mature RBC? | 16 |
| How long does the maturation process in the bone marrow take? | 5 to 7 days |
| Polychromatophil erythrocytes circulate for approximately how long before maturation is completed? | 24 -48 hours |
| What is the life cycle of a mature RBC? | 120 days |
| What happens to senescent erythrocytes? | They are removed from circulation by splenic macrophage phagocytosis. |
| Erythropoietin hormone comes from what gland? | The endocrine gland |
| Where is erythropoietin synthesized? | The kidney |
| Erythropoietin is released from the kidney in response to (increased or decreased) oxygen tension? | Decreased |
| A cell must possess what in order to respond to EPO? | An EPO receptor |
| Which developing stage of erythropoiesis does not have an EPO receptor? | Polychromatophillic erythrocyte |
| What 3 growth factors play a role in erythropoiesis? | Erythropoietin, IL-3, and GM-CSF |
| What does GM-CSF stand for? | Granulocyte/monocyte colony stimulating factor |
| What is IL-3 produced by? | Activated T-cells (TH1 & TH2) |
| GM-CSF is produced by ______ & _______? | T-cells and endothelial cells |
| GM-CSF promotes (proliferation or differentiation) in the presence of (EPO or IL-3) | Proliferation; EPO |
| The rate of erythropoiesis is governed by what? | The rate of oxygen transport to the tissues |
| What 4 things does oxygen transport to the tissues depend on? | 1. Concentration of hemoglobin in the blood 2. Cardiac output 3. Oxygen saturation of hemoglobin 4. Hemoglobin's affinity of oxygen |
| EPO production is affected by what 4 hormones? | 1. Testosterone 2. Glucocorticoids 3. Thyroxine 4. Growth hormone |
| The hormones which affect EPO production have a direct or indirect relationship with EPO? | Direct |
| What is effective erythropoiesis? How do we measure this? | A representation of the number of viable, functional RBC's available; reticulocyte count |
| What is total erythropoiesis? How is it measured? | A representation of erythroid precursors in the bone marrow; myeloid:erythroid ratio as well as bone marrow cellularity |
| What is a normal myeloid:erythroid ratio? | 3:1 |
| How do we measure ineffective erythropoiesis? | Total erythropoiesis - effective erythropoiese |
| As a mature RBC, the nucleus contracts as chromatin condenses into a functionless _________ which is finally extruded. | pyknotic mass |
| Does a mature RBC contain protein synthesizing organelles and mitochondria? | No |
| The stage of erythrocyte accumulates a full complement of hemoglobin. | A mature erythrocyte |