The nose is the most prominent projection of the face whose function is to provide a portal for air to enter and exit the body. Dry external air is moisturized so as not to dry out the airway and lungs. It is made of the outer covering (skin), a support system (cartilage and bone), and lining (mucosa). The cartilage is the softer floppy structure that permits movement and control of the opening of the nostrils. The nasal bones support the bridge of the nose between the eyes. The septum is the wall between the two nostrils that is a sandwich of cartilage and bone surrounded by mucosa. It functions like a tent pole holding up the lower nose. Deeper in the nose opposite the septum, turbinates project into the air flow to humidify the air. The turbinates enlarge and shrink depending on the needs for moisture. Under the turbinates are the holes into the sinuses.
The nasal airway can be obstructed by: thickened mucosal lining of nose (such as in a cold or allergies), a deviated septum, a thickened septum, distorted external nasal structures and thickened or enlarged turbinates. Sinus obstruction can also occur from local swelling of the turbinates. Deviation of the septum and nasal deformities can increase the chance of this obstruction such that a smaller swelling closes off the openings that otherwise would be open.