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What Is the Piriform Sinus?

By Shelby Miller
Updated Mar 03, 2024
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The piriform sinus, also commonly spelled pyriform sinus, is a feature of the pharynx, or human throat. It is contained in the hypopharynx, which is the lower portion of the pharynx that is found between the hyoid bone on the front of the neck and the lower border of the cricoid cartilage where the larynx, or voice box, begins. The piriform sinus is a narrow fossa, or depression, situated to either side of the opening to the larynx. It is a common site of hypopharyngeal cancers, with nearly 70 percent of cancers afflicting the lower throat occurring here.

Beginning immediately behind the nasal and oral cavities, the pharynx or throat consists of three sections. The nasopharynx, also known as the upper or epipharynx, links the nasal cavity to back of the mouth. Situated behind the tongue is the middle section, the meso- or oropharynx, where the mouth opens to the throat. The lowest portion of the pharynx is the hypopharynx or laryngopharynx, which begins behind the hyoid bone, a U-shaped bone to which the muscles of speech and swallowing attach. Running downward toward the larynx, it ends where the flap of soft tissue known as the epiglottis closes off the larynx — the path to the trachea and lungs — from the esophagus during the act of swallowing.

The hypopharynx can be subdivided into three sections: the posterior pharyngeal wall, the postcricoid area, and the piriform sinus. Above the esophagus in the back of the throat is the posterior pharyngeal wall, while the postcricoid area lies forward, within the space beyond the opening of the epiglottis to the larynx and behind the posterior wall of the cricoid cartilage of the larynx. Forming the lateral or side portion of the hypopharynx, visible when viewed from the front, is the piriform sinus. It forms a pair of teardrop-shaped recesses that drop down on either side of the epiglottis where it opens to the larynx. Not uncommonly, food that is not swallowed properly can get stuck in this space, increasing the risk that it will be aspirated, or enter the trachea instead of the esophagus.

Also of clinical significance is the frequency of pharyngeal cancer in the piriform sinus. While only a third of hypopharyngeal cancers are found in the postcricoid and posterior pharyngeal regions, nearly 70 percent are located in the piriform sinus. These cancers tend to be squamous cell carcinomas, and they tend to afflict people who have previously been frequent users of tobacco and/or alcohol.

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Discussion Comments

By Feryll — On Dec 16, 2014

Have you ever heard anyone say that something went down the wrong pipe when they are eating? Well, in many cases what happens is food or water gets trapped in the piriform sinus. My doctor told me this is what was happening to me when I was experiencing coughing attacks while eating.

His advice was for me to slow down and not gulp drinks or swallow such large pieces of food. It's also important to breathe normally during meals.

By mobilian33 — On Dec 16, 2014

@Animadel - A friend of mine recently found out that the cause of her neck infections is related to the pyriform sinus. She had a really bad infection and she had lesions as well. Of course, this really scared her, and the first thing she thought of was that she probably had some type of mouth cancer. She was able to get over the infection, and thankfully she didn't need surgery.

By Animandel — On Dec 15, 2014

I have a friend who is a nurse. She works in a doctor's office. They had a patient who came in and said she was having a problem with bad breathe. She had really bad breathe sometimes and she didn't know what was causing the condition. She tried mouthwash, flossing, brushing, chewing gum, mints and some home remedies, but none of them worked to get rid of the odor.

They ran tests at the doctor's office and then the doctor also recommended that she see a dentist. All the tests and the visit to the dentist didn't produce any diagnosis as to the cause of the woman's chronic bad breathe.

She went to an oral specialist, and it was eventually determined that when she ate, food was getting trapped in her mouth. And the primary place where the food was getting lodged was in the piriform sinus. And of course, when food gets stuck in your mouth, bacteria starts to attack the bits of food and this cause a foul odor.

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