7.2

• Internal non-specific defences: phagocytosis (monocytes, macrophages, neutrophils, dendritic cells)

  • inflammatory response
  • lymphatic system
• Phagocytic cells:

  • monocytes and macrophages
  • neutrophils
  • dendritic cells
• Monocytes and macrophages:

  1. tissue becomes infected/inflamed
  2. monocytes enter the bloodstream and differentiate into macrophages
  3. some macrophages moves through the tissue to destroy pathogens
  4. others are fixed in one place and destroys pathogens that crosses them

  • macrophages are important in removing microbes and dying cells
• Neutrophils:

  • granulated leucocyte (granules visible in cytoplasm)
  • has a lobulated nucleus
  • accounts for 55-70% of all leucocytes
  • first cells to move into the tissue in an infection
  • important in killing pathogens inside cells
  • life span: a few days
  • dead cells makes up a large portion of pus
• Dendritic cells:

  • characterised by projections from the cytoplasm
  • function goes beyond phagocytosis
  • can detect, engulf and process foreign particles
  • uses info to assist with specific immunity
• Inflammatory response:

  • pain
  • redness
  • swelling
  • heat
• Purpose of inflammation:

  • reduce spread of pathogens
  • remove damaged tissue and cell debris
  • begin repair of damaged tissue
• Proteins from the complement system assisted certain steps of the inflammatory response
• Steps of inflammatory response:

  • chemical/mechanical damage → mast cells activated
  • activation releases histamine, heparin and other chemicals into tissue fluid
  • complement system proteins and some chemicals attract phagocytes
  • pain receptors are triggered
• Histamine:

  • increases blood flow (vasodilation) → redness and heat
  • capillaries more permeable → more fluid diffuses into the tissue
  • fluid escaping from blood → swelling
  • pus formed by dead phagocytes
  • new cells prod. and repair of tissue occurs
• Heparin:

  • prevents clotting in immediate area of injury
  • clot of fluid forms → spread of pathogen slows
• Fever:

  • infection that elevates body temperature
  • increased temperature → inhibits growth of some bacteria and viruses and speed up rate of chemical reactions
  • pyrogens - agent causing fever that is released by leucocytes
• Lymphatic system:

  • certain bacteria trapped in the meshwork of fibres
  • infection occurs → lymphocyte formation increases