Barriers against the infection:
1. Skin- It is the first line of defence (physical) which prevents invasion by microorganisms. Skin protects the body unless it is damaged, by an injury or burn.
2. Mucous membranes- It is a barrier that envelops the mouth, nose, and eyelids. Tears, mucus and saliva are a part of this defence and they contain enzymes that break down the cell wall of many bacteria.
3. The digestive tract-Beside its main function, it can be an effective barrier, because of stomach acid, pancreatic enzymes, bile, and intestinal secretions. These components can kill bacteria or prevent their multiplying.