THE PARANASAL SINUSES

The sinus cavities are spaces filled with air that lie within the bony skeleton of your face. They are lined by a mucous membrane and are in continuity with the nasal passage.

There are 4 pairs of sinuses:

  • Frontal Sinuses:
    • Pair of air filled cavities behind your forehead
    • Communicate with the nasal passages through a small opening at the bottom of each sinus
  • Maxillary Sinuses:
    • Pair of air filled cavities behind your cheekbones; below your eyes and above your teeth
    • Largest pair of sinuses
    • Communicate with the nasal cavity through a small opening at the entrance of each sinus
  • Ethmoid Sinuses:
    • Multiple small air cells shaped like a honeycomb behind your nose and between your eyes
    • They form 2 main groups of cells: anterior and posterior ethmoidal cells
  • Sphenoid Sinuses:
    • Pair of air filled cavities in the center of your head
    • Communicate with the nasal passages through a small opening at the front of each sinus
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Why do we have sinuses?

The functions of the sinus cavities are:

  • Humidify and heat the air you breathe
  • Help your immune system filter the air that enters your nose
  • Increase the resonance of your voice
  • Protect the important structures of your head from trauma (like an airbag)
  • Decrease the weight of the bones of your face
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How do they work?

Healthy sinuses are filled with air and have a very thin mucous membrane lining called respiratory epithelium.

The air you breathe should flow freely from your nose, through the small openings and in and out of your sinuses.

If these natural openings are blocked, the air can’t circulate and the thin membrane becomes inflamed and thicker. Your sinuses can then fill up with fluid, pus, or nasal polyps