Tonsil, name applied to any of a number of masses of lymphoid tissue forming a ring around the walls of the pharynx, or throat. These masses consist of cells, similar to the lymphocytes of the bloodstream, embedded in fibrous connective tissue and covered by a single layer of epithelium. The lymphoid cells are phagocytic (see Phagocytosis) and help protect the pharynx from invasion by disease-producing bacteria. Tonsils may become inflamed and acutely or chronically infected. Such a condition, called tonsillitis, is often caused by streptococcus infection. Tissues surrounding the tonsils frequently form pus during acute attacks of tonsillitis, particularly streptococcal, causing the tonsils to show white specks or even be coated with whitish exudate. This condition is called quinsy. Pharyngeal tonsils, located at the back of the throat, may become abnormally large when inflamed. They are called adenoids. Acute cases of tonsillitis are often treated by administration of such antibiotics as penicillin. Chronic recurrent tonsillitis may be treated by surgical removal of the tonsils, a procedure that is known as tonsillectomy.