Now, let's go into our mouth. Inside our mouth we essentially produce a special type of proteolytic enzyme known as a lysosome. And the lysosome is also produced by our eyes. And what the lysosome essentially does is it breaks down the cell walls of bacterial cells killing off those bacteria. So in our saliva and in our tears we find this proteolytic enzyme called lysozyme which essentially kills off bacterial cells. Now let's move into our passageways the air passageways of our body.