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Masses of lymphoid nodules comprising tonsils are collected in three general locations in the wall of the pharynx. (a) Palatine tonsils are located in the posterior lateral walls of the oral cavity, and lingual tonsils are situated along the surface of the posterior third of the tongue. Both are covered with stratified squamous epithelium. The pharyngeal tonsil is a single medial mass situated in the posterior wall of the nasopharynx. It is usually covered by ciliated pseudostratified columnar epithelium, but areas with stratified epithelium can also be observed. Hypertrophied regions of pharyngeal tonsils resulting from chronic inflammation are called adenoids. (b) A sectionSource: showing several14. lymphoid nodules (LN),&collectively coveredJunqueira’s by stratifiedBasic squamous epithelium (E) on one side and a connective tissue Chapter The Immune System Lymphoid Organs, Histology, 13e capsule (CT)Citation: on the other. Some nodules show lighter staining germinal centers (GC). Infoldings of the mucosa in some form crypts (C), along Mescher AL. Junqueira’s Basic Histology, 13e; 2013 Available at: http://mhmedical.com/ Accessed: Maytonsils 03, 2017 which nodules are especially numerous. Lumens of crypts contain desquamated epithelial cells, live and dead lymphocytes, and bacteria. X140. H&E. Copyright © 2017 McGraw-Hill Education. All rights reserved (c) Epithelium (E) surrounding tonsillar crypts (C) often becomes infiltrated with lymphocytes and other leukocytes and can become difficult to recognize histologically. Adjacent connective tissue at the top of the photo also contains numerous lymphocytes. X200. H&E.