Disease

• Infectious diseases


  Caused by pathogens (disease-causing organisms)
• Non-infectious diseases


  Not caused by pathogens and cannot be caught from another person
• Pathogens


  Parasites that live in or on another organism (the host) and cause them harm
• Some pathogens are large enough to be seen without a microscope, e.g. tapeworms, however most are too tiny to see with the naked eye
• Many diseases are caused by single-celled bacteria, protozoa or fungi
• Viruses and prions are not big enough to be seen with a light microscope but they cause serious illness
• When you 'catch' a disease from someone the pathogen that they are carrying invades your body as well
• First line of defence


  Preventing the pathogen from entering the body
• Second line of defence


  Inflammation around an infection, increased blood flow, white blood cells sent to the area
• Third line of defence


  Specific targeting of pathogens, unlike the non-specific first and second lines
• First line of defence


  • Physical barriers (skin, coughing, sneezing, cilia, nasal hairs)
  • Chemical barriers (saliva, tears, stomach acid, acidic vaginal mucus)
• Skin


  • Waterproof, dry, slightly acidic, cuts heal fast
• Mucous membrane


  • Creates mucus in which microbes get trapped
• Respiratory system


  • Tiny hairs called cilia beat and sweep mucus out of the body, coughing brings mucus up to be swallowed
• Second line of defence


  • Increased blood flow, white blood cells (phagocytes) that engulf and destroy pathogens, fevers
• • Prions
  • Mad cow disease
• • Viruses
  • Influenza
  • Measles
  • AIDS
  • Chickenpox
• • Bacteria
  • Botulism
  • Tetanus
  • Tuberculosis
  • Cholera
• • Fungi
  • Ringworm
  • Tinea
  • Thrush
• • Animals
  • Louse
  • Liver fluke
  • Tapeworm 
• • Protozoa
  • Malaria 
  • Giardiasis
• Non-infectious diseases are not caused by pathogens and you cannot catch a non-infectious disease from another person.
• • Nutritional 
  • Anaemia
  • Obesity
  • Osteoporosis
  • Goitre
• • Inherited 
  • Cystic fibrosis
  • Colour blindness
  • Haemophilia 
• • Mental
  • Depression
  • Schizophrenia
• • Chemical(metabolic)
  • Lactose intolerance
  • Diabetes
• • Environmental
  • Drug related
  • Accident related
  • Asbestos related
• • Cancer
  • Stomach
  • Colon
  • Breast
• • Ageing
  • Heart
  • Arthritis 
• Pathogens are parasites that live in or on another organism(the host) and cause them harm.
• • The first and second lines are described as non-specific as they target all pathogens the same, however the third line of defence is referred to as specific because it targets all pathogens differently. 
• • Some of the white blood cells are phagocytes. Phagocytes can engulf and destroy pathogens. 
• Lymphocytes


  A special type of white blood cell that is part of the third line of defence when pathogens get past the first and second lines of defence
• Antigen


  A foreign particle that stimulates an immune response, including parts of bacteria, viruses and other pathogens
• Immune response to antigen

  Lymphocytes start to divide
• Types of lymphocytes


  • B lymphocytes
  • T lymphocytes
• B lymphocyte division


  Plasma cells are produced
• Plasma cells


  Produce antibodies which are proteins that bind with particular antigens
• Antibodies


  • Some make antigens clump together so they can be more easily engulfed by phagocytes
  • Others react to other antigens differently
  • Each antibody is highly specific and can only work on one antigen
• The first time your body is exposed to an antigen, it takes from 10 - 17 days for antibodies to be produced at peak levels