Sinuses: What are they and what do they do?


There are a variety of issues that can affect our sinuses, and for most people, the only time we really become aware of the sinuses are when they are acting up. It may never have occurred to you to ask: What, exactly, are your sinuses, anyway?

The origins of the term

“Sinus” is Latin for “curve” or “fold.” In anatomy, the word is used to refer to a system of hollow cavities.  While there are many sinuses in the body, typically, the word “sinus” refers to those around your nose and eyes that are connected to the nose.1

The sinuses extend through the cheekbones, the forehead, behind the nose, and between the eyes. There are a few different sinuses, and they are all interconnected.2

  • in the cheekbones are the maxillary sinuses, the largest of the sinuses. There is one opening in each cheek.
  • in the bone of the forehead, above the bridge of the nose, are the frontal sinuses—one per side.
  • the ethmoid sinuses are between the eyes, behind the bone at the inside corner of each eye, and are structured like a honeycomb.
  • the sphenoid sinuses are located farther back, behind the ethmoid sinuses.

The sinuses’ function

These sinus cavities are lined with soft tissue, and they’re usually empty. The walls of the sinus cavities are lightly coated with mucus, which keeps the tissue moist and healthy, and also traps bacteria.3 As air passes through the sinus passages on the way to the lungs, the mucus helps humidify and filter the air.

Have you experienced any of the following symptoms for 12 consecutive weeks or longer and are over the age of 18?

  • Facial pain, pressure, or fullness
  • Difficulty breathing through nose
  • Descreased sense of smell
  • Drainage of cloudy or colored mucus
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In addition, the sinuses help the voice resonate, and can affect the way we perceive someone’s speech.4 That is, the shape, volume, and health of the sinuses influence how “nasal” we perceive someone’s voice to be.5

The sinuses need to be able to drain regularly and freely in order to clear mucus and to function properly. If this drainage gets blocked, sinus problems result.

You and your sinuses

Your sinuses are a complex system, and they’re important for your health and comfort. If your sinuses aren’t working properly—if they’re inflamed, swollen, uncomfortable, producing an abnormal discharge—and the symptoms don’t go away on their own quickly, it might be time to see an ENT physician. Visiting a medical professional is the surest way to get help for your sinuses. Talk to your doctor for more information.




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The purpose of the site is to help create awareness about sinusitis and treatment options for the disease. Please note that information contained on this site is not medical advice. It should not be used as a substitute for speaking with your physician. Always talk with your physician about diagnosis and treatment information.