Hematopoiesis and Stem Cells
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Questions and Answers

What is the term given to the cells that are regulated by certain hormones or substances to proliferate and undergo maturation?

  • Erythrocyte
  • Haemopoietic stem cells
  • Normoblasts
  • Progenitor cells (correct)

    • What is the term given to the formation or genesis of red blood cells?

  • RBC Development
  • Haemopoiesis
  • CFU-E Formation
  • Erythropoiesis (correct)

    • What is the regulator of BFU-E, which gives rise to thousands of nucleated erythroid precursor cells?

  • Colony Stimulating Factor
  • Erythropoietin
  • Haemopoietic factor
  • Burst Promoting Activity (BPA) (correct)

    • At which stage of erythropoiesis does the nucleus condense and Hb appears?

    <p>Intermediate normoblast</p> Signup and view all the answers

    What is the size of a mature red blood cell?

    <p>7.2µm</p> Signup and view all the answers

    At which stage of erythropoiesis does the nucleus become pyknotic and Hb is maximum?

    <p>Late normoblast</p> Signup and view all the answers

    What percentage of cells in the bone marrow belong to the myeloid series?

    <p>75%</p> Signup and view all the answers

    What is the characteristic of stem cells that allows them to differentiate into any blood cell lines?

    <p>Pluripotency</p> Signup and view all the answers

    What is the term for the supporting system formed by the bone marrow and spleen?

    <p>Hematopoietic microenvironment</p> Signup and view all the answers

    What type of stem cells can convert into any tissue type?

    <p>Totipotent stem cells</p> Signup and view all the answers

    What is the term for the process by which stem cells give rise to new stem cells?

    <p>Self-renewal</p> Signup and view all the answers

    What is the term for the process by which stem cells differentiate into specific blood cell lines?

    <p>Commitment</p> Signup and view all the answers

    What is the term for the precursor cells that give rise to megakaryocytes, lymphocytes, erythrocytes, eosinophils, and basophils?

    <p>Progenitor cells</p> Signup and view all the answers

    What happens to committed stem cells as they lose their capacity for self-renewal?

    <p>They become irreversibly committed</p> Signup and view all the answers

    What is the characteristic feature of a Pronormoblast?

    <p>Basophilic cytoplasm with polyribosomes</p> Signup and view all the answers

    What is the distinctive feature of a Polychromatophilic normoblast?

    <p>Presence of chromatin lumps</p> Signup and view all the answers

    What is the characteristic feature of an Orthochromatic normoblast?

    <p>Small and pyknotic nucleus</p> Signup and view all the answers

    What is the characteristic feature of a Reticulocyte?

    <p>Reticular nuclear fragments</p> Signup and view all the answers

    What is the duration of the differentiation phase from a Pronormoblast to a Reticulocyte?

    <p>5 days</p> Signup and view all the answers

    What is the feature of maturation phase from Reticulocyte to RBC?

    <p>Reduction in size</p> Signup and view all the answers

    What is the percentage of Reticulocytes in total red cells?

    <p>1-2%</p> Signup and view all the answers

    What is the characteristic feature of Erythrocytes?

    <p>Presence of hemoglobin</p> Signup and view all the answers

    What is the primary site of erythropoietin production?

    <p>Kidneys</p> Signup and view all the answers

    What is the primary function of erythropoietin?

    <p>To stimulate the production of red blood cells</p> Signup and view all the answers

    What is the effect of hypoxia on erythropoiesis?

    <p>It increases erythropoiesis</p> Signup and view all the answers

    What is the role of vitamin B12 in erythropoiesis?

    <p>It is essential for DNA synthesis and RBC maturation</p> Signup and view all the answers

    What is the effect of vitamin B12 deficiency on red blood cells?

    <p>It produces macrocytic anemia</p> Signup and view all the answers

    What is the role of intrinsic factor in erythropoiesis?

    <p>It is involved in vitamin B12 absorption</p> Signup and view all the answers

    What is the effect of iron deficiency on erythropoiesis?

    <p>It decreases erythropoiesis</p> Signup and view all the answers

    What is the role of catecholamines in erythropoiesis?

    <p>They stimulate erythropoiesis</p> Signup and view all the answers

    What is the result of hypothyroidism on erythropoiesis?

    <p>Decreased erythropoiesis</p> Signup and view all the answers

    What is the function of the liver in erythropoiesis?

    <p>Storage of vitamin B12, folic acid, iron, and copper</p> Signup and view all the answers

    What is the effect of androgens on erythropoiesis?

    <p>Increase erythropoiesis</p> Signup and view all the answers

    What is the result of bone marrow destruction on erythropoiesis?

    <p>Decreased erythropoiesis</p> Signup and view all the answers

    What is the function of haematopoietic growth factors in erythropoiesis?

    <p>Regulate the proliferation and differentiation of progenitor stem cells</p> Signup and view all the answers

    What is the result of hypoxia on erythropoiesis?

    <p>Increased erythropoiesis</p> Signup and view all the answers

    What is the result of Cushing's disease on erythropoiesis?

    <p>Increased erythropoiesis</p> Signup and view all the answers

    What is erythrocytosis?

    <p>An increase in RBC count</p> Signup and view all the answers

    Study Notes

    Hematopoiesis

    • Normally, 75% of bone marrow cells belong to the myeloid series, which produces white blood cells, while 25% are maturing red cells
    • Despite this, there are over 500 times more red cells in the circulation than white cells

    Stem Cells

    • Hematopoietic stem cells (HSCs) have extensive proliferative capacity and the ability to:
      • Give rise to new stem cells (self-renewal)
      • Differentiate into any blood cell lines (pluripotency)
    • HSCs differentiate into committed stem cells (progenitor cells), which in turn form various types of blood cells

    Clonal Hemopoiesis

    • Pluripotent stem cells multiply and commit to specific cell lines, forming progenitor cells
    • Progenitor cells regulate the proliferation and maturation of specific blood cells

    Progenitor Cells

    • Committed stem cells lose their capacity for self-renewal and become irreversibly committed to specific cell lines
    • Progenitor cells are regulated by hormones or substances, allowing them to:
      • Proliferate
      • Undergo maturation

    Erythropoiesis

    • Erythropoiesis is the process of red blood cell formation
    • Stages of RBC development:
      • Pluripotential hematopoietic stem cell
      • Committed stem cell
      • Proerythroblast
      • Early, intermediate, and late normoblasts
      • Reticulocytes
      • Erythrocytes

    Stages of RBC Maturation

    • Pronormoblast:
      • 15-20µm in size
      • Basophilic cytoplasm
      • Nucleus with nucleoli
      • No hemoglobin
    • Basophilic normoblast:
      • Large nucleus
      • Basophilic cytoplasm
      • Active mitosis
      • Slightly reduced in size
    • Polychromatophilic normoblast:
      • Chromatin lumps
      • Hb starts appearing
      • Reduced mitoses
    • Orthochromatic normoblast:
      • Small and pyknotic nucleus
      • Eosinophilic cytoplasm
      • Mitoses absent
    • Reticulocyte:
      • Reticular nuclear fragments
      • Nucleus extruded
      • Slightly larger than RBCs

    Erythrocytes Production

    • Process of erythropoiesis takes 5 days from pronormoblast to reticulocyte phase
    • Maturation phase from reticulocyte to RBC takes 2 days
    • Features of RBC maturation:
      • Reduction in size
      • Disappearance of the nucleus
      • Acquisition of hemoglobin

    Control of Erythropoiesis

    • Erythropoiesis is stimulated by erythropoietin hormone
    • Stimulated by:
      • Hypoxia (low oxygen)
      • Anemia
      • Hemorrhage
      • High altitude
      • Lung disease
      • Heart failure

    Erythropoietin

    • Glycoprotein hormone produced mainly by the kidneys (90%) and liver (10%)
    • Stimulates erythropoiesis by acting on committed stem cells to induce proliferation and differentiation of erythrocytes in bone marrow
    • Site of action: bone marrow

    Factors Affecting Erythropoiesis

    • Hormonal factors:
      • Androgens
      • Thyroid hormones
      • Glucocorticoids
      • Pituitary gland
      • Haematopoietic growth factors
    • Nutritional requirements:
      • Amino acids
      • Iron
      • Vitamin B12 and Folic acid
      • Vitamin C
      • Proteins

    Clinical Aspects

    • Anemias: reduced RBC count or reduced Hb concentration
    • Polycythemia: increased RBC count
    • Erythrocytosis: increased RBC count due to hypoxia

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    Description

    This quiz covers the process of blood cell formation and the characteristics of stem cells, including their ability to self-renew and differentiate into various blood cell lines.

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