Ref: Grays Anatomy, 40th ed., Dhingra PL. s ENTExplanation:BOUNDARIESThe laryngopharynx is situated behind the entire length of the larynx (known clinically as the hypopharynx) and extends from the superior border of the epiglottis, w'here it is delineated from the oropharynx by the lateral glossoepiglottic folds, to the inferior border of the cricoid cartilage, where it becomes continuous with the oesophagus.The laryngeal inlet lies in the upper part of its incomplete anterior wall, and the posterior surfaces of the arytenoid and cricoid cartilages lie below this opening.Pyriform fossaA small pyriform fossa lies on each side of the laryngeal inlet, bounded medially by the aryepiglottic fold and laterally by the thyroid cartilage and thyrohyoid membrane.Branches of the internal laryngeal nerve lie beneath its mucous membrane.At rest, the laryngopharynx extends posteriorly from the low:er part of the third cervical vertebral body to the upper part of the sixth.During deglutition it may be elevated considerably by the hyoid elevators.Inlet of larynxThe obliquely sloping inlet of the larynx lies in the anterior part of the laryngopharynx and is bounded above by the epiglottis, below by the arytenoid cartilages of the larynx, and laterally by the aryepiglottic folds,Below the inlet, the anterior wall of the laryngopharynx is formed by the posterior surface of the cricoid cartilageThe hypopharynx is clinically subdivided into three regions: the pyriform sinus. Post cricoids region, and posterior pharyngeal wall.Pyriform fossae are smooth depressions on either side of the larynx, acting as passages that guide swallowed food into the esophagus avoiding the larynx.Sensory innervations to pyriform sinus is internal laryngeal nerveMost common foreign body to get impacted in pyriform sinus is fish boneThe postericoid region is the part of the hypopharynx directly behind the cricoid cartilage. Cancers often occur in the hypopharynx.Carcinoma in the region of pyriform sinus remains silent until it reaches cervical group of lymph nodes.