The sinuses are four pairs of hollow, air-filled, enclosed spaces that lie behind your cheeks, eyebrows, and jaw.
The maxillary sinuses lie behind your eyes and under your cheeks. The frontal sinuses are above your eyes and behind your forehead.
The ethmoid sinuses — a honeycomb-like mesh of 6 to 12 small spaces — lie between your eyes on each side of your nose, and the spheroid sinuses lie behind your nose.
Structure of the Sinuses
Membranes with tiny hairs called cilia line the sinuses, and each sinus has an opening (or an ostium) into either side of the nose, which is divided into two halves by the septum.
Ridges of thin, rounded tissue covered by membrane (called turbinates or concha) line the wall of each side of the nose. Air flows though each side of the nose, and the turbinates help filter and humidify air in the nose.
Each sinus also drains into spaces between each turbinate (called the meatus).
Sinuses are present in most other mammals, as well as in birds and some reptiles. The sinuses help to improve the sense of smell in some animals (e.g. dogs, hyenas, and tigers). And like humans, domestic animals such as dogs, cats, and horses can also get sinusitis.
Function of the Sinuses
The sinuses protect the nasal passages and keep them moist by filtering unwanted particles out of the air we breathe.
The membranes that line each sinus are filled with cilia and cells that make fluid called mucus.
The cilia collect and sweep out pollutants, micro-organisms, dust, and dirt into the mucus, which moves toward the throat. We usually swallow the mucus.
In addition to moderating the temperature and humidity of the air we breathe, some researchers believe the sinuses might also:
- Lighten the weight of the skull
- Provide resonance for the voice
- Protect the brain, especially against blows to the face
There is not very much evidence to support these theories, however. Researchers agree that the function of the sinuses remains a bit of a puzzle.
Doctors Who Treat Sinus Conditions
Different physicians treat sinus conditions.
If you have sinusitis, a primary care physician might treat you. If you have sinusitis caused by allergic rhinitis, you may need to see an allergist. Infectious disease specialists treat acute bacterial sinusitis.
If your child has a sinus condition, you will need to see a pediatrician.
Otolaryngologists (ear, nose and throat specialists) perform surgery to correct paranasal abnormalities or to drain the sinuses.
Sinus Cancer and Other Sinus Conditions
Inflammation of the ethmoid sinuses, known as ethmoiditis, usually follows a cold and can affect children from the age of 3. This potentially serious condition is treated with antibiotics.
Nasal and ethmoidal polyps can grow from the sinuses, causing nasal blockage and catarrh (a buildup of excess mucus). Polyps are usually surgically removed.
Cancer may also affect the sinuses. The most common type of sinus cavity cancer is squamous cell carcinoma, which affects the cells that line the inside of the sinuses and nose.
Risk factors for sinus cancers include exposure to certain workplace chemicals, being infected with human papillomavirus virus (HPV), being male, being older than 40, and smoking.
Last Updated: 8/21/2014