Collections of lymphoid tissue in the mucosa of the pharynx surrounding the openings of the nasal and oral cavities (Waldeyer’s tonsillar ring) are part of the body’s defense system. The largest of these collections form distinct masses (tonsils). Tonsils occur mainly in three areas (Fig. 8.205):
The pharyngeal tonsil, known as adenoids when enlarged, is in the midline on the roof of the nasopharynx.