hematopoeisis

• The department of Hematology studies blood, blood-forming tissues, and disorders associated with them

  • Blood is a special type of fluid connective tissue derived from mesoderm
  • Plasma is a pale yellow colored liquid component of blood that holds the cellular elements of blood in suspension
• Functions of plasma:

  • Absorbs, transports and releases heat
  • Osmotic balance
  • Defense mechanism
  • Blood clotting
  • PH buffering
• Functions of blood:

  • Deliver oxygen and nutrients to all body cells
  • Transport waste products from cells for elimination
  • Transport hormones
  • Maintain body temperature, PH, fluid volume
  • Prevent blood loss (clotting)
  • Prevent infection (WBCs, antibodies)
• Hematopoiesis is the production of all cellular components of blood and blood plasma

  • Occurs within the hematopoietic system, including bone marrow, liver, and spleen
  • Hematopoiesis is the process through which the body manufactures blood cells
• Theories on blood cell formation:

  • Monophyletic theory: all blood cells come from origin stem cell, the HEMOCYTOBLAST REC
  • Polyphyletic theory: different groups of blood cells originate from different stem cells
• Extra medullary hematopoiesis refers to hematopoiesis occurring outside of the bone

  • Can be physiologic or pathologic
  • Physiologic EMH occurs during embryonic and fetal development in the liver and spleen
  • Pathologic EMH can occur in adulthood when physiologic hematopoiesis can’t work properly in bone marrow (Pathologic EMH can be caused by myelofibrosis thalassemia or disorders caused in the hematopoietic system.)
• Hematopoiesis in bone marrow:

  • Hematopoietic stem cell differentiates into Common lymphoid progenitor cell (CLP) and Common Myeloid progenitor cell (CMP)
  • Growth factors control the growth and reproduction of stem cells
• (Cluster of differentiation) CD-markers are cell markers used in immunophenotyping

  • CD markers help differentiate cell types based on molecules present on their surface, These markers are often used to associate cells with certain immune functions.
  • CD markers are used in basic research and disease diagnosis, such as specific types of leukemia and lymphoma.
• B lymphocytes:

  • Generated in bone marrow and mature in spleen
  • B cell receptor binds to antigens
  • Activated B cells differentiate into plasma cells for antibody production
• T cells:

  • Generated in bone marrow and mature in thymus
  • T cell receptor recognizes processed antigens
  • Differentiate into Cytotoxic T cells, Helper T cells, Memory T cells, Suppressor T cells
• Natural killer cells:

  • Efficient cell killers targeting abnormal cells
  • Distinguish between normal and abnormal cells based on MHC class 1 expression
• Interleukins are solvable glycoproteins that modulate cellular behavior

  • Synthesized by helper CD4 T lymphocytes, monocytes, macrophages, and endothelial cells
  • Promote development and differentiation of T and B lymphocytes
• Differentiation of myeloid progenitor cell:

  • Myeloblast, Promyelocyte, Myelocyte, Metamyelocyte, Band neutrophil granulocyte, Segmented neutrophil granulocyte
• Differentiation of myeloid progenitor cell:

  • Eosinophil granulocyte, Basophil granulocyte, Lupus Erythematosus cell
• Differentiation of myeloid progenitor cell producing promonocytes:

  • Monocytes differentiate into macrophages and dendritic cells
• Erythropoiesis is governed by Erythropoietin produced by the kidneys

  • RBC maturation program includes Pro normoblast, Basophilic normoblast, Polychromatic erythroblast, Orthochromic normoblast, Reticulocyte, Mature erythrocyte
• Reticulocytes are immature RBCs released into circulation after maturation in the marrow

  • Reticulocyte count helps diagnose anemia types
• Erythropoietin is secreted by the kidney to stimulate RBC production in response to hypoxemia
• Platelets are small cell fragments in blood that form clots and prevent bleeding
• Hemocytoblast gives rise to BC (erythrocytes), WBC (leukocytes), and platelets
• Monocytes, lymphocytes, and plasma cells are derived from tissue hemocytoblast
• Lymphoblast:

  • Nucleus is round or oval
  • Fine granular chromatin
  • One or more indistinct nucleoli
• Prolymphocyte:

  • Nucleus is round
  • Contains a single prominent nucleoli
  • More cytoplasm than a lymphoblast
  • Chromatin is more condensed
• Lymphocytes:

  • Small (7-10 µm) and round in shape
  • Large nucleus
• Plasma cell:

  • Round or oval
  • Coarsely clumped chromatin
  • Main function is to produce antibodies
• LE cell (Lupus Erythematosus cell) is a neutrophil or macrophage that has phagocytized the denatured nuclear material of another cell
• LE cell is a diagnostic test for systemic Lupus Erythematosus (SLE) based on an in vitro immunologic reaction between the patient’s autoantibodies to nuclear antigens and damaged nuclei in the testing medium