Nasopharynx

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Pharyngeal mucosa and related structures.

The nasopharynx is the uppermost region of the pharynx located directly behind the posterior nasal apertures (choanae) and superior to the level of the soft palate. Its roof and posterior wall are formed by mucosa overlying the base of the skull, specifically the body of sphenoid bone and the basal part of the occipital bone. The nasopharynx also serves as the posterior extension of the nasal cavity and permits free passage between it and the nasal cavities. The rigid roof, posterior and lateral walls of the nasopharynx create a vaulted space that is always open.

The posterolateral walls of the nasopharynx are unique in that they bear the openings of the auditory (Eustachian) tubes. These openings lie above the level of the hard palate and connect the nasopharynx to the middle ear cavity on both sides. A fold of mucosa called the tubal elevation (torus tubarius) surrounds each opening forming a bulge on the pharyngeal wall. Behind this tubal elevation lies a deep recess called the pharyngeal recess.

The nasopharyngeal cavity opens into the cavity of the oropharynx through the pharyngeal isthmus, which lies between the posterior border of the soft palate and the posterior pharyngeal wall. This region is marked on the posterior pharyngeal wall by a fold of mucosa formed by the palatopharyngeal sphincter between the palatopharyngeus muscle and the superior pharyngeal constrictor muscle. During swallowing, elevation of the soft palate and constriction of the palatopharyngeal sphincter seals off the pharyngeal isthmus, separating the nasopharynx from the oropharynx. This prevents the retrograde flow of materials into the nasopharynx and nasal cavity.

The roof of the nasopharynx contains a large collection of lymphoid tissue within the mucosa called the pharyngeal tonsil which are often clinically referred to as the adenoids when enlarged. A small collection of lymphoid tissue called the tubal tonsil, often lies in the mucosa just behind the opening of the auditory tube.