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[L. tonsilla, almond]

1. A mass of lymphoid tissue in the mucous membranes of the pharynx and base of the tongue. The free surface of each tonsil is covered with stratified squamous epithelium that forms deep indentations, or crypts, extending into the substance of the tonsil. The palatine tonsils, pharyngeal tonsils (adenoids), and lingual tonsils form a ring of immunologically active tissue.
2. A rounded mass on the inferior surface of the cerebellum lying lateral to the uvula.

Tonsils detect and respond to pathogens entering the body through the mouth and nose. Inflammation of the tonsils (tonsillitis) occurs during upper respiratory infections caused by common viruses. Beta-hemolytic streptococci or, occasionally, Staphylococcus aureus infections may occur as primary infections or follow viral infections, most commonly in children and immunocompromised adults. Clinically, the patient will have enlarged, reddened, tender glands, often coated with inflammatory exudate, which may form a pseudomembrane. The tonsils may stay enlarged after multiple infections and are sometimes surgically removed (tonsillectomy).
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INFLAMED TONSILS Source: Centers for Disease Control and Prevention

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