Sinuses

The sinuses are hollow cavities within the facial bones. Sinuses are not fully developed until after age twelve. When people speak of sinus infections, they are most frequently referring to the maxillary and frontal sinuses.

Sinusitis

Sinusitis refers to inflammation of the sinus cavities, which are moist, hollow spaces in the bones of the skull. There are four pairs of sinuses:

• Frontal sinuses
• Maxillary sinuses
• Ethmoid sinuses
• Sphenoid sinuses (not shown in illustration)

If the opening from a sinus cavity becomes plugged, the flow of mucus is blocked and pressure builds up, causing pain and inflammation.

Chronic Sinusitis

The sinuses are surrounded by bone and cartilage and lined with a mucous membrane. Sinusitis occurs when the membranes becomes inflammed and painful, which may be a result of a blocked sinus opening.

Chronic sinusitis is often caused by inflammation and blockage due to physical obstruction such as a deviated septum, misformed bone or cartilage structures such as the nasal conchae (turbinates), or blockage by nasal cysts or polyps.