Pyriform sinus

Pyriform sinus refers to the pear-shaped fossa (Latin for “trench”) just lateral to the laryngeal entrance. Its medial surface is the aryepiglottic cord; laterally it is bounded by the thyroid cartilage, and posteriorly by the low posterior pharyngeal wall. The pyriform fossas and post-arytenoid area together constitute the “swallowing crescent,” which channels swallowed material just before it enters the esophagus, behind the larynx.