On either side of the laryngeal

Larynx

The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...

 orifice is a recess, termed the piriform sinus (also piriform recess, pyriform sinus, or piriform fossa), which is bounded medially by the aryepiglottic fold

Aryepiglottic fold

The entrance of the larynx is a triangular opening, narrow in front, wide behind, and sloping obliquely downward and backward. It is bound, in front, by the epiglottis; behind, by the apices of the arytenoid cartilages, the corniculate cartilages, and the interarytenoid notch; and on either side,...

, laterally by the thyroid cartilage

Thyroid cartilage

The thyroid cartilage is the largest of the nine cartilages that make up the laryngeal skeleton, the cartilage structure in and around the trachea that contains the larynx....

 and hyothyroid membrane

Hyothyroid membrane

The hyothyroid membrane is a broad, fibro-elastic layer, attached below to the upper border of the thyroid cartilage and to the front of its superior cornu, and above to the upper margin of the posterior surface of the body and greater cornua of the hyoid bone, thus passing behind the posterior...

. The fossae are involved in speech.

The term "piriform," which means "pear-shaped," is also sometimes spelled "pyriform" (as in the diagram on this page.)

Deep to the mucous membrane of the piriform fossa lie the recurrent laryngeal nerve

Recurrent laryngeal nerve

The recurrent laryngeal nerve is a branch of the vagus nerve that supplies motor function and sensation to the larynx . It travels within the endoneurium...

 as well as the internal laryngeal nerve

Internal laryngeal nerve

The internal laryngeal nerve is the internal branch of the superior laryngeal nerve. It descends to the thyrohyoid membrane, pierces it in company with the superior laryngeal artery, and is distributed to the mucous membrane of the larynx....

, a branch of the superior laryngeal nerve

Superior laryngeal nerve

The superior laryngeal nerve is a branch of the vagus nerve. It arises from the middle of the ganglion nodosum and in its course receives a branch from the superior cervical ganglion of the sympathetic....

. The internal laryngeal nerve supplies sensation to the area, and it may become damaged if the mucous membrane is inadvertently punctured.

The piriform sinus is a subsite of the hypopharynx

Hypopharynx

In human anatomy, the hypopharynx is the bottom part of the pharynx, and is the part of the throat that connects to the esophagus....

. This distinction is important for head and neck cancer staging

Cancer staging

The stage of a cancer is a description of the extent the cancer has spread. The stage often takes into account the size of a tumor, how deeply it has penetrated, whether it has invaded adjacent organs, how many lymph nodes it has metastasized to , and whether it has spread to distant organs...

 and treatment.

Clinical significance

It is a common place for food to become trapped; if foreign material becomes lodged in the piriform fossa of an infant, it may be retrieved nonsurgically. If the area is injured (eg., by a fish bone), it can give the sensation of food stuck in the throat.

The persistency of the piriform sinus (specially on the left side) is a common cause of acute thyroiditis in children and adolescents.