The pyriform sinus, also known as the piriform recess or piriform fossa, is a pear-shaped anatomical space in the throat that plays a part in the complex process of swallowing. This structure is one of several components that guide food and liquids safely through the digestive tract.
Anatomical Location
The pyriform sinus is a small, pear-shaped depression situated on both sides of the laryngeal inlet, which is the opening to the voice box or larynx. It forms part of the hypopharynx, the lowest section of the pharynx or throat. Each sinus is a distinct channel that begins at the level of the pharyngoepiglottic fold.
The boundaries of the pyriform sinus are well-defined by surrounding structures. Medially, it is bordered by the aryepiglottic fold, a fold of mucous membrane that separates the sinus from the epiglottis. Laterally, the sinus is bounded by the thyroid cartilage, often referred to as the Adam’s apple, and the thyrohyoid membrane. The superior extent of the pyriform sinus is at the level of the hyoid bone, while its inferior extent reaches the level of the inferior border of the cricoid cartilage. These fossae, along with the post-arytenoid area, collectively form what is sometimes called the “swallowing crescent,” which funnels material just before it enters the esophagus, located behind the larynx.
Role in Swallowing
The primary function of the pyriform sinus is to facilitate the safe and efficient passage of food and liquids from the mouth to the esophagus during swallowing. Its unique pear-shaped, gutter-like structure acts as a channel, directing the swallowed material, or bolus, away from the airway and into the digestive tract. This design prevents aspiration, the accidental entry of food or liquid into the trachea (windpipe) and lungs.
During swallowing, various muscles and structures coordinate to ensure the bolus moves effectively. The pyriform sinuses help guide the bolus around the entrance of the larynx, bypassing the airway. If the upper esophageal sphincter (UES), a muscular valve at the top of the esophagus, does not open adequately, material may remain in the pyriform sinuses, increasing the likelihood of aspiration after the swallow. The coordinated action of pharyngeal muscles, including the constrictors, also helps to propel food and water through the laryngopharynx and into the esophagus.
Clinical Importance
The pyriform sinus is medically significant due to its role in swallowing and its susceptibility to various conditions. It is a common location where foreign bodies can become lodged. If foreign material becomes trapped, it can cause discomfort and may require medical intervention. Pooling of saliva or other secretions in the pyriform sinuses can also occur, which may indicate issues with swallowing function and can increase the risk of aspiration into the lungs.
This area is also a frequent site for cancerous growths. Pyriform sinus cancer is a type of head and neck cancer that originates in this region. Due to their hidden location, tumors often remain without noticeable symptoms until they reach a more advanced stage. Medical professionals often examine the pyriform sinuses during endoscopic procedures to check for abnormalities like inflammation, masses, or structural changes.
Symptoms that might suggest a problem in this area include:
- Difficulty swallowing (dysphagia)
- Painful swallowing (odynophagia)
- Persistent sore throat
- Referred ear pain
- Changes in voice
- The presence of a lump in the neck