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Questions and Answers
What controls the relative rates of red blood cell production in the bone marrow?
What controls the relative rates of red blood cell production in the bone marrow?
Which type of stem cell is categorized as multipotent in hematopoiesis?
Which type of stem cell is categorized as multipotent in hematopoiesis?
Which colony-forming unit is specific for megakaryocytes?
Which colony-forming unit is specific for megakaryocytes?
Which of the following is not a type of granulocyte?
Which of the following is not a type of granulocyte?
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What role do erythrocytes play in the body?
What role do erythrocytes play in the body?
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Which colony-forming unit is responsible for producing both granulocytes and monocytes?
Which colony-forming unit is responsible for producing both granulocytes and monocytes?
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At what stage do stem cells begin differentiating into specific blood cell types?
At what stage do stem cells begin differentiating into specific blood cell types?
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What type of stem cells give rise to B lymphocytes?
What type of stem cells give rise to B lymphocytes?
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Which of the following statements about megakaryocytes is true?
Which of the following statements about megakaryocytes is true?
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Which stage marks the first appearance of hemoglobin in erythrocyte development?
Which stage marks the first appearance of hemoglobin in erythrocyte development?
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Which of the following statements regarding growth inducers is true?
Which of the following statements regarding growth inducers is true?
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What occurs to the nucleus of erythrocytes during maturation?
What occurs to the nucleus of erythrocytes during maturation?
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Which condition is characterized by the presence of smaller, pale red blood cells?
Which condition is characterized by the presence of smaller, pale red blood cells?
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What is the role of differentiation inducers in blood cell formation?
What is the role of differentiation inducers in blood cell formation?
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What type of anemia is indicated by the abnormal production of erythrocytes?
What type of anemia is indicated by the abnormal production of erythrocytes?
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Which erythrocyte precursor is the most mature stage before becoming an erythrocyte?
Which erythrocyte precursor is the most mature stage before becoming an erythrocyte?
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What role does erythropoietin play in red blood cell production?
What role does erythropoietin play in red blood cell production?
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How does hypoxia influence erythropoietin secretion?
How does hypoxia influence erythropoietin secretion?
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What happens to red blood cell production when the kidneys are removed?
What happens to red blood cell production when the kidneys are removed?
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What is the primary regulator of red blood cell production according to the given information?
What is the primary regulator of red blood cell production according to the given information?
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Which statement about erythropoietin production during high altitude exposure is accurate?
Which statement about erythropoietin production during high altitude exposure is accurate?
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Which substance is mentioned as stimulating erythropoietin production?
Which substance is mentioned as stimulating erythropoietin production?
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What is the effect of x-ray therapy on the bone marrow in relation to erythropoiesis?
What is the effect of x-ray therapy on the bone marrow in relation to erythropoiesis?
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What is indicated by the maximum production time frame of erythropoietin?
What is indicated by the maximum production time frame of erythropoietin?
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What is the primary site of RBC production during the last month of gestation and after birth?
What is the primary site of RBC production during the last month of gestation and after birth?
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Which type of cell serves as the origin for all circulating blood cells?
Which type of cell serves as the origin for all circulating blood cells?
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At what age does the production of RBCs start to decline significantly in long bones?
At what age does the production of RBCs start to decline significantly in long bones?
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Which organs produce reasonable numbers of RBCs during the first trimester of gestation?
Which organs produce reasonable numbers of RBCs during the first trimester of gestation?
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Which bones continue to produce RBCs into adulthood?
Which bones continue to produce RBCs into adulthood?
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What happens to the marrow of long bones as a person ages?
What happens to the marrow of long bones as a person ages?
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What keeps the supply of multipotential cells available in the bone marrow?
What keeps the supply of multipotential cells available in the bone marrow?
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What is a characteristic of the marrow in long bones after about the age of 20 years?
What is a characteristic of the marrow in long bones after about the age of 20 years?
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What is the main protein that iron combines with in the cytoplasm to form ferritin?
What is the main protein that iron combines with in the cytoplasm to form ferritin?
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How does the body regulate total body iron when it becomes saturated?
How does the body regulate total body iron when it becomes saturated?
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What form does iron take in the storage pool when it is present in extremely insoluble clusters?
What form does iron take in the storage pool when it is present in extremely insoluble clusters?
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What happens to the absorption rate of iron when stores become depleted?
What happens to the absorption rate of iron when stores become depleted?
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How long do red blood cells typically circulate before being destroyed?
How long do red blood cells typically circulate before being destroyed?
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What is transferrin's unique characteristic in iron transport?
What is transferrin's unique characteristic in iron transport?
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Ferritin can store what type of iron in varying amounts?
Ferritin can store what type of iron in varying amounts?
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What happens to the rate of iron absorption when there is a low quantity of iron in plasma?
What happens to the rate of iron absorption when there is a low quantity of iron in plasma?
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What happens to the cardiac output in a person with anemia during exercise?
What happens to the cardiac output in a person with anemia during exercise?
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What is a common outcome when a person with polycythemia exercises?
What is a common outcome when a person with polycythemia exercises?
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What factor can influence blood viscosity in individuals with polycythemia?
What factor can influence blood viscosity in individuals with polycythemia?
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Which of the following is a key characteristic of secondary polycythemia?
Which of the following is a key characteristic of secondary polycythemia?
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How does polycythemia typically affect arterial pressure?
How does polycythemia typically affect arterial pressure?
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What physiological change occurs to blood when an individual experiences tissue hypoxia?
What physiological change occurs to blood when an individual experiences tissue hypoxia?
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What is a result of the body's pressure-regulating mechanisms during polycythemia?
What is a result of the body's pressure-regulating mechanisms during polycythemia?
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Which statement about the skin's color in polycythemia vera is correct?
Which statement about the skin's color in polycythemia vera is correct?
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Study Notes
Red Blood Cells (Erythrocytes)
- Major function: Transport hemoglobin, which carries oxygen from lungs to tissues.
- Hemoglobin remains inside RBCs in humans for effective transport.
- RBCs contain carbonic anhydrase, speeding up CO2 and water reaction to carbonic acid, facilitating CO2 transport.
- Hemoglobin is a good acid-base buffer, playing a role in blood pH balance.
- Shape: Biconcave disc, about 7.8 micrometers in diameter and 2.5 micrometers thick at thickest point, 1 micrometer or less in the center.
- Size: Average volume is 90-95 cubic micrometers.
- Shape flexibility: RBCs can change shape to squeeze through capillaries, preventing rupture.
- Concentration in blood: Healthy men: 5,200,000 (±300,000) RBCs/cubic millimeter; Healthy women: 4,700,000 (±300,000) RBCs/cubic millimeter. Higher at high altitudes.
- Hemoglobin concentration: Up to 34 g/100 ml of cells; maintaining this level prevents exceeding metabolic capacity.
- Normal hematocrit (percentage of blood comprised of cells): 40-45%
- Hemoglobin content: Normal men: 15 g/100 ml blood; Normal women: 14 g/100 ml blood.
- Oxygen-carrying capacity: Each gram of hemoglobin can combine with 1.34 ml of oxygen (when saturated).
- Production of RBCs:
- Embryonic weeks: Yolk sac, liver.
- Mid-gestation: Liver primary production area.
- Later gestation/after birth: Exclusively in bone marrow.
- Bone marrow production: All bones until age 5; long bones stop around age 20; other bones gradually decrease in production over time.
Genesis of Blood Cells
- Multipotential hematopoietic stem cells (MHSCs): Origin of all blood cells.
- Committed stem cells (CFU): Differentiated cells, committed to a specific type of blood cell.
- CFU-E (Colony forming unit-erythrocyte): forms erythrocytes.
- CFU-GM (Colony forming unit-granulocytes, monocytes).
- CFU-M (Colony forming unit-megakaryocytes): forms megakaryocytes.
Production of Red Blood Cells
- Erythropoietin: A glycoprotein hormone, primarily produced by the kidneys (90%).
- Function: Stimulates production of proerythroblasts from hematopoietic stem cells.
- Stimulation: Regulation of total mass of RBCs. Maintains appropriate levels to carry sufficient oxygen without hindering blood flow.
- Hypoxia: Low oxygen levels in tissue stimulate erythropoietin production.
- Kidney function: Renal tissue hypoxia increases HIF-1 levels, leading to erythropoietin gene transcription.
Maturation of Red Blood Cells
- Proerythroblast: Early cell in RBC line.
- Basophil erythroblast: Earliest generation, stains with basic dyes.
- Polychromatophil erythroblast: Contains hemoglobin.
- Orthochromatic erythroblast: Contains significant amount of hemoglobin, nucleus condenses, and then gets extruded.
- Reticulocyte: Still has some residual cytoplasmic organelles and is transitional form from bone marrow to blood.
- Erythrocyte (Mature RBC): No nucleus, final stage.
Tissue Oxygenation
- Condition: Low tissue oxygen level increases RBC production.
- Causes: Hemorrhage, x-ray therapy to bone marrow, high altitudes, decreased tissue blood flow, and certain lung and heart diseases.
Maturation Failure Anemia / Pernicious Anemia
- Deficiency: Lack of absorption of Vitamin B12.
- Causes: Atrophic gastric mucosa (i.e., decreased intrinsic factor)
- Effects: Leads to abnormal and reduced DNA synthesis, resulting in abnormally large RBCs.
Folic Acid Deficiency Anemia
- Deficiency: Lack of folic acid absorption.
- Causes: Small intestinal disease or sprue; insufficient folic acid ingestion; cooking methods.
- Effect: Insufficient DNA synthesis, resulting in abnormally large RBCs.
Hemoglobin Formation
- Chemical steps: Formation involves succinyl CoA, glycine, pyrrole, protoporphyrin IX, iron, and polypeptide chains (a and b).
- Structure: Four polypeptide chains bind loosely to form the hemoglobin molecule, enabling oxygen binding.
Iron Metabolism
- Function: Hemoglobin, myoglobin, cytochromes, and other compounds require iron (4-5 grams in body).
- Storage: Primarily ferritin, deposited in hepatocytes and reticuloendothelial cells (liver, spleen, bone marrow).
- Transport: Iron combines with apotransferrin to form transferrin, carried in plasma for delivery to cells.
Life Span of Red Blood Cells
- Lifespan: ~120 days in circulation.
- Destruction: When damaged cells rupture and release hemoglobin, it's engulfed by macrophages.
- Macrophages process hemoglobin, release iron, and recycle components.
Anemias
- Blood Loss Anemia:
- Acute: Plasma and RBCs restored in 1-3 days with fluid balance.
- Chronic: Iron absorption inadequate to make up for blood loss = microcytic, hypochromic anemia.
- Aplastic Anemia: Bone marrow failure secondary to various causes.
- Megaloblastic Anemia: Impairment in RBC maturation due to Vitamin B12 / Folic acid deficiency.
- Hemolytic Anemia: RBC fragility causes premature destruction (e.g., hereditary spherocytosis, sickle cell anemia, erythroblastosis fetalis).
Polycythemia
- Secondary Polycythemia: Excess RBC production due to chronic hypoxia.
- Can be caused by altitude differences or lung/heart/circulatory issues.
- Polycythemia Vera (Erythremia): Pathological condition.
- Abnormal RBC production.
Effects of Anemia and Polycythemia on Circulation
- Anemia: Low blood viscosity due to reduced RBC count = increase in cardiac output.
- Polycythemia: Increased blood viscosity due to greater RBC concentration = reduced venous return. Regulation maintains normal cardiac output.
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Description
This quiz explores the structure and function of red blood cells (RBCs), highlighting their role in oxygen transport and carbon dioxide management. It covers aspects such as hemoglobin content, shape flexibility, and concentration in the blood. Test your knowledge about these vital components of the circulatory system.
