Mucous membrane

The mucous membranes are tissues which excrete a thick moist mixture known as mucus (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 mucus is constantly moved by cilia in the bronchial passages to the throat, where it's either expelled or taken into the stomach.
The mucous membrane in the stomach protects the stomach lining from stomach acid, but allows the absorption of water and nutrients. The lack of mucus can lead to gastritis or ulcerations.
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 mucus 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 mucus and can no longer take in oxygen.
In patients with cystic fibrosis, the mucus 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.
Mucous membrane at Wikipedia
Category:Anatomy