Picture of the Sinuses

Human Anatomy

Medically Reviewed by Sabrina Felson, MD on July 10, 2020

Picture of the Human Sinuses

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The sinuses are a connected system of hollow cavities in the skull. The largest sinus cavities are about an inch across. Others are much smaller.

  • Your cheekbones hold your maxillary sinuses (the largest).
  • The low-center of your forehead is where your frontal sinuses are located.
  • Between your eyes are your ethmoid sinuses.
  • In bones behind your nose are your sphenoid sinuses.

They’re lined with soft, pink tissue called mucosa. Normally, the sinuses are empty except for a thin layer of mucus.

The inside of the nose has ridges called turbinates. Normally these structures help humidify and filter air. A thin wall, called the septum, divides the nose. Most of the sinuses drain into the nose through a small channel or drainage pathway that doctors call the “middle meatus.”

Why do we have sinuses? Experts don’t know. One theory is that they help humidify the air we breathe in. Another is that they enhance our voices.

Sinus Conditions

Acute sinusitis (sinus infection): Viruses, bacteria, or fungi infect the sinus cavity, causing inflammation. More mucus; nasal congestion; discomfort in the cheeks, forehead, or around the eyes; and headaches are common symptoms.

Chronic sinusitis (or chronic rhinosinusitis): More than just a series of infections, chronic sinusitis is a persistent process of inflammation of the sinuses.

Deviated septum: If the septum that divides the nose is too far too one side, it can obstruct airflow in a nostril.

Hay fever (allergic rhinitis): Allergens like pollen, dust mites, and pet dander cause the defenses in the nose and sinuses to overreact. Mucus, nasal stuffiness, sneezing, and itching result.

Nasal polyps aresmall growths in the nasal cavity. They can happen due to inflammation from asthma, chronic sinus infections, and nasal allergies (such as hay fever).

Turbinate hypertophy: The ridges on the nasal septum are enlarged, which can block airflow.

Sinus Tests

Physical examination: A doctor can look into the nose with a lighted viewer to see the turbinates, which may be swollen. They may press or tap on the face over the sinuses to check for pain.

Computed tomography (CT scan): A CT scanner uses X-rays and a computer to create detailed images of the sinuses. CT scanning can help diagnose chronic sinusitis.

Magnetic resonance imaging (MRI): Magnetic waves create highly detailed images of the sinuses. You may get CT and MRI scans.

Rhinoscopy: Doctors use a flexible tube with a camera on its end to see inside your nose and sinuses.

Sinus cultures: Your doctor uses a needle to take a mucus sample from inside your sinuses.

Skin test for allergies: These help to see if allergies are involved in your sinusitis.

Sinus X-ray: A plain X-ray may show problems with the bones around the sinuses. A CT scan is better.

Sinus Treatments

Antibioticsmay be needed to treat bacterial sinusitis.

Antihistamines: Medicines that can reduce the nasal and sinus symptoms from allergic rhinitis.

Decongestants: Drugs that cause blood vessels in the inner nasal tissue to constrict. As a result, there is less sinus congestion, mucus, and postnasal drip.

Nasal saline spray: Salt water (saline) nasal spray breaks up dried mucus and helps to keep the nose moist.

Nasal steroid spray: These medications ease tissue swelling and help prevent the regrowth of nasal polyps after sinus surgery.

Nasal washes: They rinse mucus from the nasal cavities and sinuses.

Sinus surgery can improve or correct some sinus conditions. Doctors use it to remove growths or to open a blockage.

Show Sources


Porter, G. Paranasal Sinus Anatomy and Function, January 2002.

Johns Hopkins Medicine: “Sinusitis.”

American Academy of Allergy, Asthma, and Immunology: “Nasal Polyps."

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