Blood cells

• Haematology


  The study of the blood, including its composition and function

  
• Functions of blood

  • Transportation
  • Regulation
  • Protection

  
• Blood composition


  • Plasma (55%)
  • Erythrocytes (RBCs)
  • Leukocytes (WBCs)
  • Thrombocytes (platelets)

  
• Hematocrit


  The percentage of blood volume consisting of erythrocytes (red blood cells)

  
• Plasma components


  • Ions
  • Nutrients
  • Metabolic waste products
  • Hormones
  • Enzymes
  • Antibodies
  • Proteins (albumins, globulins, fibrinogens)
• Albumins


  The most abundant protein in plasma, produced by the liver, provides osmotic pressure to maintain blood volume
• Globulins


  Plasma proteins produced by the liver that transport lipids and fat-soluble vitamins (α and β), and antibodies produced by B-lymphocytes (γ)
• Fibrinogen


  An important clotting factor produced by the liver
• Red blood cells (RBCs)

  The most abundant cells in the body, necessary for the delivery of oxygen to the tissues

  
• RBCs


  • Transport haemoglobin
  • Contain carbonic anhydrase to form bicarbonate ion (HCO3-) from CO2 and water
• Haemoglobin

  A protein in RBCs that carries oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs
• RBC shape and size

  • Biconcave shape provides increased surface area for gas diffusion
  • Average volume of 90-95 cubic um
  • Can change shape rapidly to squeeze through capillaries
• Normal RBC concentration in blood: Men 5.2 million per cubic mm, Women 4.7 million per cubic mm
• RBC adaptations

  • Lack nuclei and mitochondria to allow more space for haemoglobin and anaerobic metabolism
  • Contain carbonic anhydrase to catalyse formation of bicarbonate ions for CO2 transport
• RBC production

  1. Embryonic life: Yolk sac

  2. Middle trimester: Liver

  3. Last month of gestation onwards: Bone marrow

  4. Up to 5 years old: All bones

  5. After 20 years: Membranous bones (vertebrae, sternum, ribs)