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What Are Sinuses?

Sinuses and Congestion

What Are Sinuses?

Sinuses are a system of interconnected hollow spaces in the skull and link to the nasal passages by small channels. Sinuses help humidify the air we breathe and enhance our voices. Air entering through the mouth and nose flows through the channels, which, like the nose, are lined with soft tissue called “mucosa.”

"Sinuses help humidify the air we breathe and enhance our voices."


By adulthood each person’s sinus pathways are unique. Everyone has four sinus cavities, each with a connection to the nasal passage:

  1. The largest are the maxillary sinuses, behind the cheekbones
  2. The frontal sinuses are in the center of the forehead
  3. The ethmoid sinuses are between the eyes
  4. The sphenoid sinuses are in bones behind the nasal cavity

Sinus Inflammation

Irritants, viral infection or allergies can all cause the mucosal tissue in the sinuses to swell. The swelling can block the channels to the nasal cavity and affect sinus drainage. This inflammation can increase the risk of a bacterial sinus infection and give the sensation of your sinus passages being congested.