Hematology

    Cards (371)

    • Blood is a specialized type of connective tissue, that is composed of plasma (fluid representing extracellular matrix) and formed blood elements (cells)
    • Blood has no fibers
    • Function of blood

      Transportation of cells and fluid
    • Formed blood elements

      • Erythrocytes (Red Blood Corpuscles)
      • Leukocytes (White Blood Cells)
      • Blood platelets
    • Leukocytes
      • Granular leukocytes: neutrophils, eosinophils and basophils
      • Agranular leukocytes: lymphocytes and monocytes
    • Tissues producing blood cells

      • Lymphoid: Spleen and lymph nodes (produces lymphocytes)
      • Myeloid: Red bone marrow (produces RBC, WBC and platelets)
    • Composition of blood after centrifugation

      • Lower red layer containing red cells (45% of whole volume)
      • Middle thin layer containing white cells & platelets (1% of whole volume)
      • Upper yellow layer containing plasma (55% of whole volume)
    • Preparation of a blood smear

      1. Spreading a drop of blood in a thin layer on a microscope slide
      2. Staining with Giemsa's stain (basic methylene blue + acidic eosin) to differentiate blood cells by their nuclei and cytoplasmic granules
    • Blood count
      Average number of a formed blood element per cubic millimeter blood (number/mm3)
    • Red blood corpuscles (RBCs)

      • Flexible biconcave discs
      • Diameter of approximately 7.5 μm
      • Hemoglobin occupies about 33% of the corpuscular volume and is more concentrated at the periphery
    • RBC shape

      • Membranous electron dense biconcave discs
      • No nucleus and no organelles
    • How RBCs adapt to function

      • Biconcave discoid shape increases surface area by 20-30%
      • Cytoskeleton helps RBCs be squeezed through narrow capillaries
      • Concentration of hemoglobin at periphery facilitates oxygen/CO2 binding
      • Selective permeability of cell membrane enhances gas exchange
    • Erythrocytes are lacking nuclei and mitochondria, relying on anaerobic glycolysis for energy
    • Anaemia
      • Reduction of haemoglobin level results in decreased oxygen carrying capacity of blood
      • Caused by defective production or increased loss of red cells
    • Types of anaemia

      • Macrocytic
      • Microcytic
      • Normocytic
    • Leukocytes (White Blood Cells)

      • Normal count 4000-10000/mm3
      • Transport from bone marrow to blood but do not function until they leave bloodstream to enter connective tissue
    • Types of WBCs

      • Granulocytes (polymorphonuclear leukocytes)
      • Agranulocytes (mononuclear leukocytes)
    • Granulocyte WBC types

      • Neutrophils
      • Eosinophils
      • Basophils
    • Agranulocyte WBC types

      • Lymphocytes
      • Monocytes
    • Neutrophils
      • Most abundant WBC (60-70%)
      • Multilobed nucleus with 2-5 segments
      • Contain two types of granules: specific granules with proteases, and azurophilic primary granules with hydrolytic enzymes and antibacterial defensins
    • During inflammatory reaction

      Neutrophils are damaged by bacterial toxins, causing their death and formation of pus
    • Eosinophils
      • Constitute 1-4% of total leukocytes
      • Characteristic bilobed nucleus
      • Responsible for regulation of allergic reactions and killing of parasites
    • Abnormal eosinophil count (eosinophilia) occurs in allergic reactions and parasitic infections
    • Bacterial toxins

      • They can bind and disrupt the cell membranes of many types of bacteria
    • Pus cells
      Neutrophils that are damaged by bacterial toxins during the inflammatory reaction, causing their death
    • Eosinophils
      Constitute only 1%-4% of total leukocytic count
    • Eosinophils
      • About the same size as a neutrophil or slightly larger, with a characteristic bilobed nucleus
    • Why are eosinophils called eosinophils?

      Because their granules have a strong affinity to the eosin component of the stain
    • Functions of eosinophils

      • Regulation of allergic reactions (secrete histaminase)
      • Killing of parasites in parasitic infections
    • Abnormal eosinophils (eosinophilia) occur in cases of allergic reactions and parasitic infections
    • Eosinophils' killing strategy

      1. Circulate in the blood
      2. Migrate to connective tissue (especially mucosa of digestive, respiratory, genital, urinary tracts and skin)
      3. Identify the enemy
      4. Proteins in granules act on forming pores on parasite surface, facilitating passage of lethal substances leading to parasite death
    • Eosinophils under light microscope

      • Nucleus: dense, bilobed, C-shaped
      • Cytoplasm: contain large, shiny reddish granules
    • Eosinophils under electron microscope

      • Cytoplasm contains two types of granules: 1) Large acidophilic specific granules with electron dense crystalloid core, contain major basic protein and histaminase enzyme 2) Small azurophilic granules contain lysosomal hydrolytic enzymes
    • Basophils
      Also called "mast cell of the blood"
    • Why are basophils called basophils?

      Because their granules have strong affinity to the basic component of the stains
    • Why are basophils called "mast cell of the blood"?

      Because they secrete heparin & histamine like the connective tissue mast cell
    • Basophils and Mast cells

      • Have surface receptors for Immunoglobulin E (IgE), and secrete their granular components in response to certain antigens and allergens
    • Basophils
      The least numerous in the blood circulation, comprising less than 1% of the leukocytes, making them difficult to find in normal blood smears
    • Functions of basophils

      • Contribute to allergic reactions by releasing histamine and heparin to produce inflammation at the allergic reaction site
    • Basophils under light microscope

      • Nucleus: bilobed, S shape, obscured by the abundant basophilic granules in the cytoplasm
      • Cytoplasm: contains abundant basophilic granules