The cilia and sticky mucus work together to protect the lungs from infection, forming what is known as a mucociliary escalator. The mucus traps any bacteria or pathogens as they enter the lungs, and the cilia, located on the surface of ciliated epithelium, move in a synchronised pattern to waft the mucus up the airway to the back of the throat where it can be swallowed and any pathogens can be killed by the acidity of the stomach.