blood

• Components of Blood


  • Red blood cells
  • White blood cells
  • Platelets
  • Plasma
• Plasma


  Over half of the volume of the blood is made up of plasma
• Red blood cells


  The majority of the other half is made up of red blood cells
• White blood cells and platelets


  The remaining fraction consists of white blood cells and platelets
• Red blood cells


  Biconcave discs containing no nucleus but plenty of the protein haemoglobin
• White blood cells


  Large cells containing a big nucleus, different types have slightly different structures and functions
• Platelets


  Fragments of cells
• Plasma


  Straw coloured liquid
• Plasma


  A straw coloured liquid which the other components of the blood are suspended within
• Substances transported in plasma


  • Carbon dioxide
  • Digested food and mineral ions
  • Urea
  • Hormones
  • Heat energy
• Carbon dioxide transport


  1. Dissolved in the plasma as hydrogencarbonate ions

  2. Transported from respiring cells to the lungs
• Digested food and mineral ions transport


  1. Dissolved particles absorbed from the small intestine

  2. Delivered to requiring cells around the body
• Urea transport


  1. Urea is dissolved in the plasma

  2. Transported to the kidneys
• Hormone transport


  1. Chemical messengers released into the blood from the endocrine organs (glands)

  2. Delivered to target tissues/organs of the body
• Heat energy transport


  1. Created in respiration (an exothermic reaction)

  2. Heat energy is transferred to cooler parts of the body or to the skin where heat can be lost
• Red blood cells


  Specialised cells which carry oxygen to respiring cells
• Red blood cells


  • Full of haemoglobin, a protein that binds to oxygen to form oxyhaemoglobin
  • No nucleus which allows more space for haemoglobin to be packed in
  • Shape is a 'biconcave disc' which gives them a large surface area to volume ratio to maximise diffusion of oxygen in and out
• White blood cells


  Part of the body's immune system
• White blood cells


  • Defend against pathogenic microorganisms
• Types of white blood cells


  • Phagocytes
  • Lymphocytes
• Phagocytes


  Carry out phagocytosis by engulfing and digesting pathogens
• Phagocytes


  • Have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells
  • Once they encounter the pathogenic cell, they will engulf it and release digestive enzymes to digest it
  • This is a non-specific immune response
• Phagocytes can be easily recognised under the microscope by their multi-lobed nucleus and their granular cytoplasm
• Lymphocytes


  • Large round nucleus taking up nearly the whole cell
  • Clear, non-granular cytoplasm
• Lymphocytes


  Produce antibodies
• Antibodies


  1. shaped proteins with a shape that is specific (complementary) to the antigens on the surface of the pathogen
• This is a specific type of immune response as the antibodies produced will only fit one type of antigen on a pathogen
• Antibody response


  1. Antibodies attach to antigens

  2. Antibodies cause agglutination (clumping together)

  3. Chemicals released that signal to phagocytes
• Agglutination


  Clumping together of pathogenic cells
• Effect of agglutination


  • Pathogenic cells cannot move very easily
• Chemicals are released that signal to phagocytes that there are cells present that need to be destroyed
• Lymphocytes


  Produce antitoxins to neutralise toxins released by pathogens
• Immunity


  The body's ability to resist a particular disease or infection
• Immune system


  • Highly complex
  • White blood cells are the main component
• Role of the immune system


  1. Prevent the infectious organism from reproducing

  2. Destroy the infectious organism
• Immunity


  • Having sufficient levels of antibodies to protect from a particular disease
  • Not suffering from the disease or its symptoms
• Stages of infection and immune response


  1. Pathogen enters blood stream and multiplies

  2. Release of toxins and infection of body cells causes symptoms

  3. Phagocytes recognise and engulf/digest pathogen (non-specific response)

  4. Lymphocyte recognises pathogen antigens

  5. Lymphocyte produces specific antibodies

  6. Lymphocyte clones itself to produce more antibody-producing cells

  7. Antibodies cause agglutination of pathogens

  8. Phagocytes engulf and digest agglutinated pathogens

  9. Patient retains antibodies and memory cells specific to the disease

  10. Secondary immune response triggered if patient encounters same pathogen again

  11. Memory cells produce large quantities of required antibody quickly
• After the patient has recovered, they retain antibodies specific to the disease as well as memory cells (lymphocytes that recognise the pathogen)
• If the patient encounters the same pathogen again, it will trigger a secondary immune response
• Memory cells can produce much larger quantities of the required antibody in a much shorter time to fight off the pathogen before the patient suffers any symptoms