[Music] when we talk about barriers to disease what we're what we're discussing is preventing pathogens from doing any damage to the body either by stopping them from getting into the body in the first place or destroying them as soon as they do get in and remember that a pathogen is just a disease causing organism and examples are things like virus and bacteria First Chemical barriers the first chemic barrier is stomach acid stomach acid is hydrochloric acid and it's got a very low PH if pathogens enter the stomach their enzymes get denatured because of the low PH environment another chemical barrier is mucus mucus is produced in a lot of parts of the body by these things called goblet cells and you can see it being produced there in yellow it's produced in for example the tra and as it's produced by the lining inside of the goblet cells it traps pathogens inside of it and then the mucus gets swept Along by these little hairlike things called cyia mechanical barriers well the first and most obvious one is the skin that's one big gigantic shield around your body to stop things from getting inside it's got a thick outer layer which is made of keratin and it's also got a sort of patch-up mechanism in place for if it ever gets broken by a cut and that is thing and that is a a blood clot another mechanical barrier is nostril hairs they basically just trap pathogens before they get a chance to enter the body so sort of thing you might get asked on in an exam maybe explain how stomach acid provides protection against disease notice that the command term is explain so the stomach contains hydrochloric acid which destroys pathogens in food give a little bit of detail a little bit of that added explanation here and it's because the low PH environment denatures the enzymes of the pathogens [Music]