The pharynx is a conduit between the nasal cavity/oral cavity and the esophagus. The pharynx represents the upper portion of the digestive tract and is lined with squamous epithelium. The pharynx is divided into three primary segments: the Nasopharynx, Oropharynx and the Hypopharynx. Cancers that occur within each of these anatomic spaces is staged differently according to the AJCC with specific treatment implications.
The nasopharynx is the superior most aspect of the pharynx. It is separated from the nasal cavity by the choana. The soft palate is the border between the nasopharynx and the oropharynx. It is inferior/anterior to the clivus. The pharyngeal tonsils(adenoids) are located within the nasopharynx. The nasophaynx connects to the temporal bone via the eustachian tube. Tumors within the nasopharynx may result in a mastoid effusion due to secondary obstruction.
The oropharynx is the central component of the pharynx and located posterior to the oral cavity in between the soft palate and epiglottis. The subsites of the the oropharynx include: the soft palate superiorly, the posterior pharyngeal wall posteriorly, the palatine tonsils laterally, the lingual tonsils inferiorly and the base of tonge anteriorly. The epiglottis is the border between the oropharynx and the hypopharynx. HPV associated head and neck cancer typically occurs within the palatine tonsils or base of tongue of the oropharynx.
There are three sets of tonsillar tissue along the phaynx: The Pharyngeal tonsils (adenoids) are located within the midline nasopharynx. The palatine (faucial) tonsils are located on either side of the soft palate. The lingual tonsils are found along the base of tongue, anterior to the valeculla.
The hypopharynx is the inferior portion of the pharynx. The subsites of the hypopharynx are the posterior pharyngeal wall below the epiglottis, the pyriform sinus and the post cricoid mucosa. The epiglottis separates the oropharynx from the hypopharynx. The aryepglottic folds separate the larynx from the hyopharynx. The hypopharynx is separated from the cervical esophagus by the cricopharyngeus muscle which is found at the inferior margin of the cricoid.
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