IH Lec

• The volume of blood in the body is 4-6 L
• The pH of blood is 7.35-7.45
• Functions of blood


  • Transport of O, CO2, nutrients, hormones, heat, and metabolic wastes
  • Regulation of pH, body temp, and water content of cells
  • Protection against blood loss thru clotting
  • Protection against diseases thru phagocytic WBCs and Abs
• Knowing the functions of blood is important for us to understand how each blood cell is being utilized in immunohematology

  
• Plasma components


  • Plasma proteins
  • Ions
  • Nutrients
  • Waste products
  • Gases
  • Regulatory substances
• Albumin


  Partly responsible for blood viscosity and osmotic pressure, acts as a buffer
• Globulins


  Transport of lipids, carbohydrates, hormones, and ions (e.g., iron and copper), Abs and complement are involved in immunity
• Fibrinogen


  Functions in blood clotting
• Ions in plasma


  • Na+, K+, Ca++, Mg++, Cl–, Fe++, PO4, H, OH–, HCO3
• Nutrients in plasma


  Glucose, AAs, triacyl glycerol, cholesterol, and vitamins, promote enzyme activity, serve as sources of energy and basic building blocks of more complex molecules

  
• Waste products in plasma

  Urea, uric acid, creatinine, ammonia salts, bilirubin
• Oxygen


  Necessary for aerobic respiration, terminal electron acceptor in electron transport chain
• Carbon dioxide


  Waste product of aerobic respiration, helps buffer blood
• Nitrogen is inert
• Enzymes


  Catalyze chemical reactions
• Hormones


  Stimulate or inhibit many body functions
• Water


  Acts as a solvent and suspending medium for blood components
• Formed elements of blood

  • Erythrocytes/RBCs
  • Leukocytes/WBCs
  • Platelets

  
• Erythrocytes/RBCs


  Transport O2 and CO2
• Leukocytes/WBCs


  • Neutrophils
  • Basophils
  • Lymphocytes
  • Monocytes
• Neutrophils


  Phagocytize microorganisms and other substances
• Basophils


  Release histamine (promotes inflammation), release heparin (prevents clot formation)
• Lymphocytes


  Produce Abs and other chemicals responsible for destroying microorganisms, contribute to allergic reactions, graft rejection, tumor control, and regulation of the immune system
• Monocytes


  Phagocytic cells in the blood, leave the blood and become macrophages (phagocytize bacteria and dead cells, cell fragments and other debris within tissues)
• Platelets


  Form platelet plugs, release chemicals necessary for blood clotting
• These components of blood can be used individually or in combination by a blood recipient depending on his/her need
• Understanding the blood cells' functions as to its application in Immunohematology could benefit the millions of blood recipients
• Areas of RBC biology crucial for normal RBC survival and function

  • Normal chemical composition and structure of the RBC membrane
  • Hemoglobin structure and function
  • RBC metabolism
• RBC membrane


  Represents a semipermeable lipid bilayer supported by a mesh-like protein cytoskeleton structure
• Layers of the RBC membrane

  • External layer (rich in glycolipids and choline phospholipids)
  • Internal layer (rich in amino phospholipids)
• Exposure of phosphatidylserine in the outer leaflet of the RBC membrane increases the cell's vascular adherence and is a signal for macrophage recognition and phagocytosis
• The normal chemical composition and the structural arrangement and molecular interactions of the RBC membrane are crucial to the normal length of RBC survival of 120 days in circulation
• 2 important RBC membrane characteristics

  • Deformability
  • Permeability
• Deformability


  To remain viable, normal RBCs must also remain flexible, deformable, and permeable
• Loss of adenosine triphosphate (ATP) (energy) levels


  Decrease in the phosphorylation of spectrin, loss of membrane deformability, accumulation of membrane calcium, increase in membrane rigidity and loss of pliability
• Permeability


  Permeability properties of the RBC membrane and the active RBC cation transport prevent colloid hemolysis and control the volume of the RBC
• RBC membrane permeability


  • Permeable to: water, anions, chloride, bicarbonate, cations (e.g., Na+, K+)
  • Impermeable to:
• RBC volume and water homeostasis are maintained by controlling the intracellular concentrations of sodium and potassium
• The active transport of sodium out of the cell and potassium into the cell is an energy-requiring process
• Calcium is also actively pumped out of the red blood cell through energy-dependent calcium-ATPase pumps