The mucous membranes are tissues which excrete a thick moist mixture known as mucous (more colloquially "snot") to protect the underlying tissues from damage. They are found in the sinus cavities, lungs and stomach. The mucous membranes in the respiratory system protect the delicate tissues from dust, bacteria and viruses, but allow the passage of oxygen. The mucous is constantly moved by cilia in the bronchial passages to the throat, where it is either expelled or taken into the stomach.
The mucous membranes require a constant supply of water to keep them moist. The drying of these membranes often leads to discomfort in breathing and in severe cases can lead to damage of the membranes. When a patient is suffering from a respiratory infection or a histamine response, the production of mucous is increased to prevent the infection from becoming established in the respiratory system. However, in severe cases, this can lead to pneumonia as the lungs fill with mucous and can no longer take in oxygen.
In patients with cystic fibrosis, the mucous produced is much thicker than normal, which interferes with breathing and digestion and provides an excellent breeding ground for bacteria, making the patient susceptible to respiratory infection. T