Study On The Histomorphology Of Tonsils In Pig

In order to investigate the histomorphology of the tonsils,the histochemical methods and transmission electron microscopy were performed on four tonsils in pig to study the anatomical localization,the distribution of antibody secreting cells(IgA and IgG secreting cells),and the ultrastructure of tonsils.The following results were obtained.1.The histomorphology of the tonsilsThe soft palatine tonsil was located on the ventral(oral) surface of the soft palate and the paraepiglottic tonsil was located bilaterally in the pharynx between the palatoglossal and the palatopharyngeal arch and formed an elevation of the pharyngeal mucosae.The soft palatine tonsil and the Paraepiglottic tonsil were both located on oropharynx tract and therefore had several similar construction features. The stratified squamous epithelium covering the tonsils consisted of numbers of cell layers.The dense connective tissue underlying the epithelium branched into the parenchyma and divided the parenchyma into many lobules.The parenchyma of the oropharynx tonsils both consisted mainly of lymph nodules and diffuse lymphoid tissue.The diffuse lymphoid tissue was constructed by reticular fibers and filled with massive lymphocytes.The pharyngeal tonsil was located in the roof of the pharynx on the caudal part of the pharyngeal septum and the tubal tonsil was located on the lateral pharyngeal wall,at the opening of the auditory tube.The pharyngeal tonsil and the tubal tonsil were situated on nasopharyngeal tract and therefore had several similar construction features.The epithelium covering the tonsils was of few cell layers which often included few goblet cells.These tonsils consisted of scattered lymph nodules,aggregations of lymphocytes and diffuse lymphoid tissue.The connective tissue distributed loosely underneath the epithelium and was infiltrated by massive lymphocytes and mast cells.Lymphatic nodules distributing closely to epithelium was observed as well.The results suggested that the anatomical localization and histological structure of the tonsils in pig may have important significances in immune defence in respiratory tract.Especially,the special features of epithelium and distribution of lymphatic nodules of the pharyngeal tonsil and the tubal tonsil suggested that the pharyngeal tonsil and the tubal tonsil may play a more important role in antigen capturing and immune response.2.Distribution of IgA and IgG secreting cells in tonsilsThe IgA and IgG secreting cells distributed in the tonsils in similar pattern.The IgA and IgG secreting cells in the pharyngeal tonsil and the tubal tonsil distributed mainly surrounding the lymph nodules.Especially,the IgA and IgG secreting cells distributing underneath the epithelium were of compact pattern.There was small quantity distribution in the lymph nodules as well.But there was almost no distribution in the basilar part of the tonsils.The IgA and IgG secreting cells in the soft palatine tonsil and paraepiglottic tonsil were all reduced significantly compared with that in the pharyngeal tonsil and the tubal tonsil.The secreting cells located mainly underneath the crypt epithelium and sparsely underneath the epithelium.The result suggested that the particular distribution of IgA and IgG secreting cells in the tonsils of pig may have special meanings in antigen capture and immune defence.3.The ultrastrueture of the tonsilsThe epithelium of the soft palatine tonsil was stratified squamous epithelium.The cell junction between the epithelial cells was clear.The intercellular junction of the epithelial cells was tight and rich in desmosomes.The collagen fiber layer underlying the epthelium was thick and separated the epithelium from the parenchyma distinctly. Massive cells of many sorts were observed in the parenchyma.The arrangement of epithelial cells of the pharyngeal tonsil was sparse and the intercellular space was loose.On the free surface of epithelial cells there were numerous microvilli.M cells and lymphocytes in the epithelium were observed as well.High endothelial venules(HEVs) were also identified in both the soft palatine tonsil and the pharyngeal tonsil.The results suggested that the HEVs may lead a good communication between local mucosal immunity of tonsils and adaptive systemic immunity of host.The particular features of epithelium and distribution of M cells in the epithelium of pharyngeal tonsil had special meanings in the immune process.The pharyngeal tonsil may play a important role in intranasal immunization.