Blood and Hemopoesis

  • Blood is a connective tissue
  • It is formed from formed elements
  • Cells
  • Platelets
  • It is suspended in extracellular matrix (plasma)
  • Blood volume in an average adult is 5-6L
  • It functions in a number of ways
  • Acid-base balance
  • Osmotic balance
  • Helps regulate body temperature
  • Plasma is composed of the following:
  • 90% water
  • 7% protein
  • fibrinogen (converts to fibrin during clotting)
  • albumin (osmotic pressure)
  • globulins (antibodies)
  • 2% amino acids
  • vitamins
  • hormones
  • 1% inorganic salts
  • serum – the yellowish fluid remaining after blood has clotted, similar to plasma but lacks fibrinogen and other clotting factors
  • mature RBC’s (erythrocytes) lack:
  • mitochondria
  • ribosomes
  • certain enzymes
  • Erythrocytes metabolize glucose for their energy needs
  • Hematocrit is (estimated percent volume of RBC’s / unit blood)
  • RBC’s are 80-90% of all blood cells
  • 33% is hemoglobin
  • anemia – low concentration of RBC’s
  • hypochromic anemia – abnormally low concentration of hemoglobin in each cell due to iron deficiency
  • pernicious anemia is due to a lack of/ or uptake problems with vitamin B12
  • polycythemia – increased concentration of circulating RBC’s
  • malaria – form of anemia
  • parasitic destruction of RBC’s
  • alterations in RBC membranes that cause aggregation and obstruction of small cerebral blood vessels
  • life span of an RBC is approximately 120 days
  • as they age, RBC’s swell and are destroyed after they are trapped in the spleen
  • peripheral proteins are associated with the internal aspect of the cell membrane
  • spectrin – maintains RBC shape
  • actin – maintains RBC shape
  • ankyrin – binds actin and spectrin to integral proteins on the cytoplasmic surface of the plasma membrane
  • leukocytes or WBC’s there are 2 types
  • agranulocytes – either lymphocytes or monocytes ; both lack granules
  • monocytes
  • 12 to 25 microns in diameter
  • filopodia
  • microvilli
  • phagosomes
  • pinocytotic vesicles
  • large nuclei, acentric and kidney shaped
  • live less than 3 days in the blood, or from months to years in connective tissue as macrophages
  • lymphocytes
  • round cells prominent nuclei
  • 20-35% of all WBC’s
  • classified as small, medium, or large
  • 2 classes

T lymphocytes – cell mediated immunity

  • Most numerous
  • Can produce lymphokines (attract macrophages)
  • Can secrete cytotoxic substances

B lymphocytes – humoral immunity

  • Can differentiate into plasma cells and secrete antibodies
  • granulocytes – characterized by the specific granules present
  • neutrophils
  • 10 to 15 microns in diameter
  • has Barr body (evagination from the nucleus)
  • granules contain:

lysozyme

collagenase

and other enzymes

functions in phagocytosing bacteria

1st line of defense

  • eosinophils
  • 12 to 16 microns in diameter
  • granules stain reddish orange
  • contains major basic protein

acts against parasitic worms

  • live for less than 2 weeks in connective tissue
  • allergic reactions and helminthic (worm) infections cause an increase in there numbers (eosinophilia)
  • corticosteroids cause a decrease
  • have an anti-inflammatory role – inactivation of histamine during allergic reactions
  • basophils
  • 10 to 15 microns in diameter
  • contain dark, large granules when stained
  • live very long time 1-1.5 years in mice
  • contain heparin and histamine
  • has an inflammatory role
  • determination is based on the presence or lack of granules
  • all leukocytes contain:
  • azurophilic granules – lysosomal in activity
  • hydrolytic enzymes
  • impart phagocytic ability
  • diapedesis is the means by which all leukocytes can cross through connective tissues and provide immunological defense
  • Platelets – cell fragments from megakaryocytes in the bone marrow
  • Hyalomere – peripheral region
  • Granulomere – central region
  • Rich in fibrinogen and PDGF (platelet-derived-growth-factor)
  • Survive about 10 days
  • Function in blood clotting
  • Hemopoesis
  • 6-8 weeks the liver and spleen as well as lymph vessels function in hemopoesis
  • 4th-6th month developing bone marrow becomes site of hemopoesis – by birth it is the only site where it occurs
  • involves mitotic division and differentiation of cells derived from pluripotent stem cells (CFU-S) ( colony forming units spleen)
  • CFU-S are present in bone marrow cords
  • Erythropoesis
  • Proerythroblast
  • Normoblast
  • Starts to produce hemoglobin
  • Reticulocyte
  • No nucleus
  • No more mitosis
  • Mature form of hemoglobin produced
  • Number of reticulocytes is dependant on physiological oxygen demand
  • It is a measure of RBC formation
  • Erythrocyte
  • Formed after ubiquitin destroys the remaining organelles
  • Granulopoesis
  • Myeloblast
  • Myelocyte
  • Band or stab cell
  • Granulocyte
  • Monopoesis
  • Monoblast
  • Differentiated mature cells
  • Monocyte
  • Macrophage
  • Lymphopoesis
  • Lymphoblast
  • Prolymphocyte
  • Lymphocyte
  • Platelet formation
  • Megakaryoblast
  • Megakaryocyte
  • Fragmentation along internal membranes called platelet demarcation channels
  • platelet

J. Maguire

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