T4.1 Haematology

• Haematology


  Study of blood and blood forming tissues, including bone marrow
• Blood


  Fluid connective tissue which circulates to and from heart through vast network of blood vessels, including arteries, veins and capillaries
• 1. 6L blood pumped through blood vessels, driven by contractions of heart
• Two extracellular fluids


  • Blood
  • Interstitial fluid
• Main functions of blood

  • Transportation
  • Regulation
  • Protection
• Blood viscosity


  Determined by number of blood cells, mainly red blood cells (most numerous type)
• Blood 'thinners' (e.g. aspirin) do not reduce blood thickness but reduce ability of blood to clot
• Blood temperature 38 degrees, pH around 7.4 (7.35-7.45)
• Blood constitutes 8% of total body weight
• Blood volume 5 to 6 litres in average, 4-5 litres in average female
• Plasma


  Blood plasma over 90% water
• Proteins in plasma

  • Albumin
  • Globulins
  • Fibrinogen
• 2% other substances in plasma: electrolytes, nutrients, hormones, gases, waste products
• Colloid


  Substance consisting of particles substantially larger than ordinary molecules but too small to be seen by unaided eye
• Colloid osmotic pressure

  Pulling power of blood
• Formed elements of blood

  • Erythrocytes
  • Leukocytes
  • Platelets
• Erythrocytes


  Most abundant formed element, making up 99%, commonly known as red blood cells or RBCs
• Leukocytes


  White blood cells or WBCs
• Two main categories of leukocytes

  • Granulocytes
  • Agranulocytes
• Platelets


  Membrane-enclosed fragments of cells which do not contain nucleus or usual organelles comprising cell
• Haemostasis


  Process of stopping bleeding (haemorrhage) following damage to blood vessel walls
• Three steps in haemostasis

  • Vascular spasm
  • Platelet plug formation
  • Blood clotting (coagulation)
• Blood clotting (coagulation)


  Cascade of chemical reactions in which each clotting favour activates the next in fixed sequences resulting in formation of fibrin meshwork
• Two pathways of blood clotting

  • Extrinsic pathway
  • Intrinsic pathway
• Blood clotting in absence of bleeding is called thrombosis - can occur in both arteries and veins
• Erythrocytes


  Shape of biconcave disks
• Haemoglobin


  Oxygen-carrying protein that constitutes about one third of erythrocytes' weight and gives blood its red colour
• Erythrocyte live only around 120 days; they wear out from bending/friction during movement through capillaries
• Haemopoiesis


  Process of erythrocyte production
• Red bone marrow produces 100 billion erythrocytes per day or 2 million per second
• Erythrocyte production requires iron, vitamin B12 and folic acid
• Blood type


  Classification of blood based on presence or absence of specific molecules called antigens which project from the surface of plasma membrane of erythrocytes
• Three important antigens that contribute to blood type

  • A antigen
  • B antigen
  • Rh protein
• ABO blood types


  • A
  • B
  • AB
  • O
• Rh blood types


  • Rh positive (Rh+)
  • Rh negative (Rh-)
• Transfusion


  Transfer of whole blood or erythrocyte concentration into bloodstream of recipient used to treat serious or severe blood loss
• Receiving incompatible blood causes antibody-antigen reaction resulting in agglutination (visible clumping) of RBCs and their destruction (lysis)
• Blood type compatibility


  • AB (universal recipients)
  • O (universal donors)
  • Rh+ and Rh-