Mohamed Zaki Helal, M.D.
Professor of ORL,
Web Page: www.mzhelal.com
Click the rectangle below to play Nasal Function Flash Movie
1- Respiratory Functions:
As a part of the airway, the nose conveys air from the outside to the nasopharynx. Neonates are obligate nose breathers; however, oral breathing can be acquired after few months if the nose is obstructed. So, a neonate would be at risk if he has bilateral complete nasal obstruction e.g. due to choanal atresia.
A certain degree of nasal resistance is normally present; this is an essential physiological function to modify the air flow pattern, to keep alveoli opened at the end of expiration and to help keeping the negative intrathoracic pressure. Additionally nasal resistance gives the feeling of air passing via the nose.
2- Protective Functions:
The nose acts as an air-conditioner for the body through the following mechanisms:
Air purification: Large particles are filtered by the nasal vibrissae. Fine particles and bacteria adhere to the mucous blanket covering nasal mucosa; this blanket is continuously driven back to nasopharynx to be swallowed. Lysozymes and immunoglobulins in nasal secretions help killing bacteria. The sneezing reflex expels irritating particles in inspired air.
Air conditioning: In cold weather, dilated blood sinusoids in submucosa act as a radiator to raise temperature of the inspired air while in hot weather, the blood sinusoids radiator function lowers the temperature of the inspired air.
Air humidification: Water in nasal secretions humidifies dry air during its passage in the nasal cavity.
Air conditioning and humidification depend on adequate wide nasal surface area achieved in the small nasal space by the highly convoluted nature of its passages.
The nasal turbinates provide this wide surface area and in addition contain most of the nasal blood sinusoids, erectile tissues and glands.
3- Olfactory Function:
Nerve endings of the olfactory nerve are present in the upper 1/3 of the nasal cavity. Air carrying odours stimulates these nerve endings while passing into the nose. Then, impulses are carried by olfactory nerve to the higher centers.
4- Phonatory Function:
Nose and sinuses act as voice resonators especially for the letters (m) and (n).
5- Drainage Function:
The nose drains tears via the nasolacrimal duct.
6- Other Functions:
Paranasal sinuses act as shock absorbants for trauma to the face and skull. They are claimed to help decreasing weight of the skull.