Located in the face and skull adjacent to the nose, the sinuses are air-filled bony cavities whose purpose is not fully understood. Some experts maintain that they exist to lighten the skull, while others note that sinuses improve vocal resonance. Most physicians believe that their chief function is to produce special mucus that keeps the inside of the nose moist and protects it from dust, dirt, pollutants, and microbiologic organisms.

There are four pairs of sinuses.

1. Frontal sinuses in the forehead region
2. Maxillary sinuses in the cheek area.
3. Ethmoid sinuses between the eyes
4. Sphenoid sinuses deep in the center of the skull

Each sinus is connected to the nose by a small opening called an ostium. All except the frontal sinuses begin growing before birth as small pockets approximately the size of a pea. They increase in size through childhood until they are about as large as a walnut.

• Learn more about sinus anatomy.
• Take the sinusitis quiz.


• Find a physician.