The mucus coating that traps micro-organisms lines the epithelium of which tracts?

1. Skin is the main physical barrier against micro-organisms. 2. Where there is no skin, mucus does the work. 3. The mucus coating lines the epithelium of the respiratory, gastrointestinal and urogenital tracts. 4. It traps micro-organisms entering the body at those openings. _Source: syllabus Biology Ch7 'Human Health and Disease', section 7.2.1_