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Localized aggregation of diffuse and nodular lymphoid tissue found in the region where the nasal and oral cavities open into the pharynx. The tonsils are important sources of blood lymphocytes. They often become inflamed and enlarged, necessitating surgical removal.
The two palatine (faucial) tonsils are almond-shaped bodies measuring 1 by 0.5 in. (2.5 by 1.2 cm) and are embedded between folds of tissue connecting the pharynx and posterior part of the tongue with the soft palate. These are the structures commonly known as the tonsils. The lingual tonsil occupies the posterior part of the tongue surface. It is really a collection of 35–100 separate tonsillar units, each having a single crypt surrounded by lymphoid tissue. Each tonsil forms a smooth swelling about 0.08– 0.16 in. (2–4 mm) in diameter. The pharyngeal tonsil (called adenoids when enlarged) occupies the roof of the nasal part of the pharynx. This tonsil may enlarge to block the nasal passage, forcing mouth breathing. See Lymphatic system