3.5 Flashcards
what is the immune system
how the body defends itself against disease causing organisms, some toxins and cancer cells
what is immunity
the ability of the body to
- resist infection by a pathogen
- destroy an organism if it invaded and infects the body
what is a pathogen
a bacterium, virus or other organism that can cause disease
what is the body’s first line of defence designed to do
prevent pathogens causing disease
what does the first line of defence consist of
- a physical barrier
- chemical secretions
what is the physical barrier made up orb
closely packed epithelial cells which can be found in the skin as well as the inner linings of the digestive and respiratory systems
what do the chemical secretion include
tears, saliva, mucus and stomach acid that are produced against invading pathogens
when does the inflammatory response kick in
when pathogens get past our first lines of defence and enter our body
what happens during the inflammatory response
histamine is released by mast cells causing vasodilation and increased capillary permeability
the increased blood flow leads to an accumulation of phagocytes and clotting elements at the site of infection
what are phagocytes
a type of wbc they recognise pathogens and destroy them by phagocytosis
what does phagocytosis involve
the engulfing of pathogens and their destruction by digestive enzymes contained in lysosomes
what do phagocytes release
cytokines
what are cytokines
a type of protein molecule that acts as a signal to attract more phagocytes and specific wbc causing them to accumulate at the site of infection
