Human Defence Systems

• Non specific defence systems include:

  • skin
  • nose
  • trachea and bronchi
  • stomach
• The cells that line the trachea also have hairs called the cilia, which are much smaller than those in the nose. These are called ciliated cells.
• Ciliated cells waft their hairs and move mucus and pathogens upwards towards the throat where it is swallowed into the stomach. Other cells called goblet cells create mucus in order to trap pathogens.
• The production of mucus in your airways is a physical barrier
• Stomach acid is hydrochloric acid which does not harm us but kills pathogens.
• The skin secretes antimicrobial substances which kill pathogens
• White blood cells travel around your blood and patrol for microbes
• White blood cells consume and digest pathogens in a process called phagocytosis
• White blood cells produce pathogens
• When some types of white blood cell come across a foreign antigen, they will start to produce proteins celled antibodies, which lock onto the invading cells so that they can be found and destroyed by other white blood cells
• The antibodies produced are specific to that kind of antigen and won't lock on to any others
• Antibodies are then produced rapidly and carried around the body to find all similar bacteria or viruses
• The white blood cells that produce antibodies are called B lymphocytes
• Some bacteria produce toxins that damage cells and tissues.

  The immune system responds to this by producing antitoxins, which neutralise the toxins released by the bacteria and prevent them form causing harm