The process of phagocytosis incudes living cells called phagocytes. These white cells are able to recognise pathogens. The phagocytes then fuse around a bacterium and engulf it within a cellular compartment called phagosome. The phagosome next fuses with a lysosome containing an acidic enzyme and chemicals that form a phagolysosome.
These then break and digest the bacterium, then the macrophage absorbs any material that can be useful and gets rid of the remaining.This is then taken away by cilia, tiny hairs that line the gaseous exchange tract. The benefits of this are that the mucus can then be swallowed and the pathogens are sent into the stomach where they are digested by enzymes and acids. The stomach acid (HCI) kills the parasite/ pathogen that has entered the body. The tears, saliva and mucus all contain an enzyme called lysozyme which breaks down the cell wall of many bacteria. This helps to instantly kill the pathogens thus preventing it from reaching the body.
Overall the benefits of these barriers are that they usually are an immediate response. They are able to immediately kill the bacteria thus protecting the body.