Blood Physiology and Erythropoiesis
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Questions and Answers

Which of these cell types is NOT involved in erythropoiesis?

  • Myoblast (correct)
  • Megakaryocyte
  • Reticulocyte
  • Proerythroblast

    • What is the primary function of mRNA in reticulocytes?

  • Encoding the synthesis of hemoglobin (correct)
  • Synthesizing ribosomal RNA
  • Regulating the rate of DNA replication
  • Transporting amino acids for protein synthesis

    • What is the significance of the retained endoplasmic reticulum in reticulocytes?

  • Increasing the cell's surface area for gas exchange
  • Supporting ongoing hemoglobin synthesis (correct)
  • Enhancing the cell's ability to engulf and destroy pathogens
  • Facilitating the production of proteins other than hemoglobin

    • At what stage of erythropoiesis does the cell lose its nucleus?

    <p>Normoblast (B)</p> Signup and view all the answers

    What is the significance of the presence of mRNA in reticulocytes?

    <p>It indicates that the cell is still capable of synthesizing proteins (C)</p> Signup and view all the answers

    Which type of hemoglobin eventually replaces fetal hemoglobin in adults?

    <p>Hemoglobin A (D)</p> Signup and view all the answers

    Which of the following substances contains iron as a key component?

    <p>Myoglobin (D)</p> Signup and view all the answers

    Which enzyme is NOT mentioned as one that contains iron?

    <p>Amylase (B)</p> Signup and view all the answers

    What is critically regulated in the context of iron metabolism?

    <p>Iron stores (B)</p> Signup and view all the answers

    Which enzyme functions primarily in cellular respiration and contains iron?

    <p>Cytochrome oxidase (B)</p> Signup and view all the answers

    What type of bond allows iron atoms to bind loosely with oxygen molecules?

    <p>Nonionic bond (C)</p> Signup and view all the answers

    What is the average molecular weight of the globin chains mentioned?

    <p>16,000 (C)</p> Signup and view all the answers

    Which of the following globin chains is NOT mentioned as a type resulting from gene duplication?

    <p>Delta (δ) (A)</p> Signup and view all the answers

    Why is it important for iron to bind to oxygen using nonionic bonds?

    <p>To facilitate release from the cell (B)</p> Signup and view all the answers

    What is a result of gene duplication regarding globin chains?

    <p>The creation of several types of globin chains (B)</p> Signup and view all the answers

    What is the primary role of intrinsic factor in relation to vitamin B12?

    <p>Binds to vitamin B12 to protect it from digestion (B)</p> Signup and view all the answers

    What condition leads to the failure of intrinsic factor production?

    <p>Atrophic gastric mucosa (D)</p> Signup and view all the answers

    How is vitamin B12 transported within the body after absorption?

    <p>By attaching to intrinsic factor for pinocytosis (A)</p> Signup and view all the answers

    Where is vitamin B12 primarily stored in the body?

    <p>Liver (D)</p> Signup and view all the answers

    What happens to vitamin B12 after it is absorbed in the ileum?

    <p>It is stored in the liver and released as needed (D)</p> Signup and view all the answers

    What is the primary role of Vitamin B12 and folate in cellular processes?

    <p>They are involved in the synthesis of thymidine triphosphate. (C)</p> Signup and view all the answers

    Why is thymidine triphosphate important for cells?

    <p>It is essential for the proliferation process of the cells. (C)</p> Signup and view all the answers

    What would likely occur if there is a deficiency in Vitamin B12 or folate?

    <p>Impaired DNA synthesis and cell proliferation. (B)</p> Signup and view all the answers

    Which biochemical compound is directly synthesized using Vitamin B12 and folate?

    <p>Thymidine triphosphate (TTP) (A)</p> Signup and view all the answers

    What cellular process is directly assisted by thymidine triphosphate?

    <p>DNA replication (C)</p> Signup and view all the answers

    What is the primary reason for the body suppressing erythropoiesis when oxygen levels reach normal?

    <p>Excess red blood cells can lead to an increase in blood viscosity, potentially disrupting blood flow. (C)</p> Signup and view all the answers

    In the context of erythropoiesis, what is the significance of the statement "the body doesn't need extra red blood cells beyond what's required"?

    <p>This implies the body strictly controls red blood cell production to avoid potential drawbacks associated with excessive numbers. (A)</p> Signup and view all the answers

    Which of the following factors is NOT directly mentioned in the context of the provided text as contributing to the regulation of red blood cell production?

    <p>The influence of hormones, particularly testosterone and estrogen. (D)</p> Signup and view all the answers

    What can be inferred from the text about the primary mechanism by which oxygen levels regulate erythropoiesis?

    <p>High oxygen levels stimulate the release of a hormone that suppresses erythropoiesis, while low oxygen levels inhibit its release. (D)</p> Signup and view all the answers

    What is the most likely consequence of the body producing an excess of red blood cells?

    <p>Increased blood viscosity, potentially leading to clots and other circulatory complications. (C)</p> Signup and view all the answers

    Study Notes

    Blood Physiology

    • Erythropoietin (EPO) is crucial for red blood cell (RBC) production.
    • Anephric individuals have a deficiency in EPO production, resulting in severe anemia.
    • The kidney is the primary site for EPO production and a small amount is produced in the liver.
    • In anephric individuals, residual EPO supports 30-50% of needed RBC production.
    • Normal hematocrit (packed cell volume) is 40-45%.
    • Anephric individuals may only achieve a hematocrit of 23-25%.
    • EPO levels increase rapidly in response to hypoxia (low oxygen).
    • RBC production takes longer than EPO level increases (days, weeks, months).
    • EPO stimulates the production of proerythroblasts from hematopoietic stem cells.
    • EPO accelerates the maturation of proerythroblasts into RBCs.
    • EPO production is regulated by a negative feedback mechanism, halting when normal oxygen levels are restored.

    Requirements for Erythropoiesis

    • Vitamin B12, folic acid, iron, and amino acids are essential for optimal erythropoiesis.
    • These nutrients are important after EPO is present.
    • Rapid cellular proliferation requires an adequate supply of these vitamins and minerals.
    • Vitamin B12 and folic acid are needed for DNA synthesis (thymidine triphosphate) to support cell division.
    • Failure in nuclear maturation leads to large, irregular RBCs (macrocytes) and increased fragility, resulting in hemolysis leading to anemia.

    Pernicious Anemia

    • Pernicious anemia is a type of megaloblastic anemia.
    • It's characterized by the production of large, bizarre, and immature RBCs by the bone marrow.
    • Causes are a failure to absorb vitamin B12 and/or produce intrinsic factor.
    • Atrophic gastric mucosa can lead to intrinsic factor deficiencies resulting in difficulties absorbing Vitamin B12.
    • Adequate vitamin B12 stores can delay symptoms of deficiencies

    Folic Acid Deficiency

    • Folic acid is found in green vegetables, fruits, and meats.
    • It is easily destroyed by cooking.
    • Deficiencies can arise from poor diet or malabsorptions in the intestine.
    • Folic acid deficiency causes similar complications to vitamin B12 deficiencies in DNA synthesis.

    Hemoglobin

    • Hemoglobin (Hgb) is crucial for transporting oxygen in RBCs.
    • Hgb consists of a peptide attached to iron.
    • Hemoglobin formation begins before RBC exit bone marrow and continues until maturation.
    • Reticulocytes, prior to maturation, contain endoplasmic reticulum and mRNA to allow for continued hemoglobin synthesis.
    • Mature RBCs have adequate hemoglobin to support 120 days of life.
    • Different types of hemoglobin exist (e.g., Fetal hemoglobin).

    Variation in Globin Chains

    • Different forms of hemoglobin have slight differences that affect oxygen binding affinities.
    • Mutations can result in abnormalities like sickle cell hemoglobin.
    • Sickle hemoglobin structure changes when exposed to low oxygen, often resulting in long crystals forming inside RBCs.
    • The changes interrupt RBC flexibility, leading to hemolysis (RBC breakdown) and vascular occlusion (blockages).

    Oxygen Binding to Hemoglobin

    • Loose iron-oxygen binding allows for smooth oxygen uptake in the lungs and release in tissues.
    • Oxygen affinity changes based on oxygen pressure and CO2 levels in the body.
    • Fetal hemoglobin has a higher oxygen affinity to support the baby's oxygen needs in utero.
    • Hemoglobin transfers oxygen as a molecule, not as an ion.

    Iron Metabolism

    • Iron is vital for hemoglobin, myoglobin and many other enzymes.
    • Total body iron is 4-5 grams, mostly in hemoglobin (around 65%).
    • Iron is stored in the body, and tightly regulated for maximal absorption.
    • Different forms exist in the body as ferritin or hemosiderin.

    Iron Transport and Storage

    • Transferrin is essential for iron transport in the blood.
    • Ferritin stores iron in cells.
    • Serum ferritin levels are used to evaluate the body's total iron stores.
    • Iron absorption happens in the small intestines.
    • Excess iron is stored as hemosiderin to prevent iron overload and toxic conditions.

    Iron Balance

    • Daily iron loss is approximately 0.6mg daily in men and 1.3mg in women
    • Iron is absorbed in the small intestine
    • The liver secretes apotransferrin, binds with free iron for transferrin transport.
    • Maximal iron absorption occurs at small amounts daily which is modulated by body iron stores.
    • RBC lifespan is 120 days

    RBC Senescence and Destruction

    • RBC lifespan lasts approximately 120 days
    • RBCs lack a nucleus, mitochondria, and endoplasmic reticulum, however contain enzymes to support ion transport.
    • Enzymes deplete with age, making the RBCs fragile, eventually leading to rupturing in the organs such as the spleen, liver.
    • Macrophages (specialized immune cells) phagocytose the ruptured cells for recycling.
    • Components (hemoglobin) are recycled to support functions in new cells

    Degradation of Hemoglobin

    • Hemoglobin is broken down into globin and heme.
    • Globin is broken down into amino acids.
    • Heme is broken down to form bilirubin.
    • Bilirubin is transported to the liver for excretion.
    • Iron is released back into the circulation or stored as ferritin.

    Anemia

    • Anemia is caused by a reduction in RBC count or haemoglobin.
    • Causes for anemia include decreased production, blood loss and/or increased destruction of RBCs
    • Conditions like iron deficiency and thalassemia are examples of anemia.
    • Methods for correcting RBC concentrations may not correct/fix the oxygen capacity of the body

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    Physiology Sheet 29 PDF

    Description

    This quiz delves into the physiology of blood, focusing on the role of erythropoietin in red blood cell production. It examines the impact of EPO levels in anephric individuals, normal hematocrit levels, and the essential requirements for erythropoiesis. Test your knowledge on how these factors contribute to overall blood health.

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