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► Health Information LibraryIn-Depth ReportsSinusitis


Sinusitis refers to inflammation of the sinus cavities, which are hollow chambers in the bones of the skull. Each sinus is lined by a membrane that produces mucus. 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.