The palatine tonsils are paired structures consisting of masses of lymphatic tissue lo-cated on either side of the pharynx. They, along with the pharyngeal tonsils (adenoids) and lingual tonsils, form a ring at the entrance to the oropharynx (Waldeyer’s ring). Structurally, the tonsils contain numerous lymphatic nodules located in the mucosa. The stratified squamous epithelium that covers the surface of the palatine tonsil (and pharyngeal) dips into the underlying connective tissue forming many crypts, the tonsi-lar crypts. The walls of these crypts contain lymphatic nodules. The epithelial lining of the crypts is typically infiltrated with lymphocytes and often to such a degree that the epithelium may be difficult to discern. While the nodules principally occupy the con-nective tissue, the infiltration of lymphocytes into the epithelium tends to mask the ep-ithelial connective tissue boundary. The tonsils guard the opening of the pharynx, the common entry to the respiratory and digestive tracts. The palatine and pharyngeal tonsils can become enflamed due to repeated infection in the oropharynx and na-sopharynx and can harbor bacteria that cause repeated infections if they are over-whelmed. When this occurs, the enflamed tonsils are removed surgically (tonsillectomy and adenoidectomy). Tonsils, like other aggregations of lymphatic nodules, do not possess afferent lymphatic vessels. Lymph, however, does drain from the tonsular lymphatic tissue through efferent lymphatic vessels. ORIENTATION MICROGRAPH: This low magnification micrograph is a section through a palatine tonsil. The hematoxylin staining areas represent the lymphatic tis-sue (L). The tonsil is surfaced by stratified squamous epithelium (SSE) which dips into the underlying connective tissue forming the tonsilar crypts (TC). At the base of one of the crypts are a number of mucous secreting glands (MG). LLLLLLMGMGTCTCTCTCSSESSELLLMGTCTCSSE
Tonsil, human, H&E, ×47.
This micrograph is from the area in the rectangle of the orientation micrograph. At this higher magnification, part of the surface epithelium (SE) of the tonsil can be readily identified. In other sites, the lymphocytes (Ly) have infiltrated the epithelium to such an extent that the epithelium is difficult to identify. The body of the nodules (N) lie within the mucosa and because of
Tonsil, human, H&E, ×365.
At the higher magnification of this micrograph, the characteristic invasiveness of the lymphocytes into the overlying epithelium is readily evident. Note on the lower left side of the micrograph a clear boundary between the epithelium and the underlying lamina propria. The basal cells (BC) of the stratified squamous epithelium can be recognized. The underlying lamina propria is occupied by numerous lymphocytes; only a few have entered the epithelial compartment. Also note the thin band of collagen fibers (CF) that their close proximity, they tend to merge. Several of the nodules have been cut in a plane that includes their germinal center (GC). Note the eosinophilic staining in these areas. Beneath the nodules is the submucosa (S) consisting of dense connective tissue, which is continuous with the dense connective tissue beyond the tonsilar tissue.