And once these pathogens are trapped inside our mucous membrane, the cilia found inside the pathogeways carry those pathogens up to the outside of our body and sometimes into our stomach. And that leads us directly to number three fluid secretions. So, why would we want any sort of pathogen to actually enter our stomach? Well, basically, if we ingest any type of food that contains a pathogen, or if the pathogens inside the mucous membrane are eventually expelled into our stomach. The reason this actually takes place is because inside our stomach we have specialized types of cells known as parietal, cells that are responsible for secreting a very acidic substance known as hydrochloric acid. And the hydrochloric acid creates a very low PH, a very acidic environment that most pathogens cannot actually survive in.