fighting disease

• our body has a very sophisticated defence system
• the human body has got features that prevent pathogens from getting into our body
• the skin acts as a barrier to pathogens - it also secretes antimicrobial substances which kill pathogens
• hairs and mucus in your nose trap particles that could contain pathogens
• the trachea and bronchi secrete mucus to trap pathogens
• the trachea and bronchi are lined with cilia - these are hair like structures, which waft the mucus up to the back of the throat where it can be swallowed
• the stomach produces hydrochloric acid - this kills pathogens that make it that far from the mouth
• your immune system can attack pathogens
• if pathogens do make it into your body, your immune system kicks in to destroy them
• the most important part of your immune system is the white blood cells
• white blood cells travel around in your blood and crawl into every part of you, constantly patrolling for microbes - when they come across an invading microbe they have three lines of attack
• the three lines of attack are: consuming the pathogens, producing antibodies and producing antitoxins
• 1 - consuming them

  white blood cells can engulf foreign cells and digest them - this is called phagocitosis
• 2 - producing antibodies

  every invading pathogen has unique molecules (called antigens) on its surface
• 2 -

  when some types of white blood cells come across a foreign antigen, they will start to produce proteins called antibodies to lock onto the invading cells so that they can be found and destroyed by other white blood cells
• 2 -

  the antibodies produced are specific to that type of antigen - they won't lock on to any others
• 2 -

  antibodies are then produced rapidly and carried around the body to find all similar bacteria viruses
• 2 -

  if the person is infected with the same pathogen again the white blood cells will rapidly produce the antibodies to kill it - the person is naturally immune to that pathogen and won't get ill
• 3 - producing antitoxins

  these counteract toxins produced by the invading bacteria