fighting disease

• the skin acts as a barrier to pathogens
• the skin also secretes antimicrobial substances which kill pathogens
• the trachea and bronchi secrete mucus to trap pathogens
• the trachea and bronchi are lined with cilia which waft mucus up to the back of the throat
• the stomach produces hydrochloric acid which kills pathogens that enter it
• the immune system destroys pathogens that make it into the body
• the immune system is made up of white blood cells, antibodies and lymph nodes
• white blood cells engulf and destroy pathogens using phagocytosis
• antibodies bind to specific pathogens and mark them for destruction by other parts of the immune system
• antibodies bind to specific pathogens and mark them as foreign so they can be destroyed by other parts of the immune system
• lymph nodes contain specialised white blood cells called lymphocytes which produce antibodies
• antibodies bind to antigens on pathogen surfaces and mark them as foreign so they can be destroyed by other parts of the immune system
• when an antigen enters the body, lymphocytes recognise it and start producing specific antibodies against it
• lymph nodes contain large numbers of white blood cells and filter out any pathogens from the bloodstream
• every invading pathogen has unique antigens on it
• if a person is infected with the same pathogen a second time, the body reacts much faster. this person is now immune to that pathogen
• antibody-producing white blood cells are called b-lymphocytes