The bronchus in the lungs are lined with hair-like projections called cilia that move microbes and debris up and out of the airways. Scattered throughout the cilia are goblet cells that secrete mucus which helps protect the lining of the bronchus and trap micron organisms.
The purpose of mucus is to lubricate and protect the organs that it lines. Mucus is supposed to be thin,clear, and watery. Cloudy, yellow, or green mucus are signs of an infection.
