Fighting Disease

• The human body has got features that stop a lot of pathogens getting inside in the first place
• 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 ligned with cilia. These are hair-like structures, which waft the mucus up to the back of the troat where it can be swallowed
• The stomach produces hydrochloric acid. This kills pathogens that make it that far from the mouth
• The immune system can attack pathogens
• If pathogens do make it into your body, your immune system tries to destroy them
• The most important part of your immune system is the white blood cells. They travel around in the blood and go into every part of the body, constantly patrolling for microbes. When they come across an invading microbe they have 3 lines of attack
• When white blood cells come across a microbe they:

  • Consume them - White blood cells can engulf foreign cells and digest them. This is called phagocytosis

  
• When white blood cells come across a microbe they:

  -Procude antibodies

  • Every invading pathogen has unique molecules (called antigens) on its surface. When some types of white blood cell 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. The antibodies produced are specific to that type of antigen - they won't lock on to any others
  • Antibodies are then produced rapidly and carried around the body to find all similar bacteria or viruses
• • If the person is infected with the same pathogen again the white blood cells with rapidly produce the antibodies to kill it - the person is naturally immune to that pathogen and won't get ill
• The white blood cells that produce antibodies are also known as B-lymphocytes
• When white blood cells come across a microbe they:

  -Produce antitoxins

  • These counteract toxins produced by the invading bacteria