The topography and the microscopic structure of tonsils in the adult bactrian camel (Camelus bactrianus)

Anatomical localisation and histology of tonsils were studied in 10 adult bactrian camels (Camelus bactrianus) aged between 5 to 10 years. Six tonsils were present: the palatine tonsil, the lingual tonsil, the tonsil of the soft palate in the oropharynx, the pharyngeal tonsil, the tubal tonsil in the nasopharynx, and the paraepiglottic tonsil in the laryngopharynx. The palatine, pharyngeal and paraepiglottic tonsils were readily visible macroscopically. They consisted mainly of secondary lymph nodules. Secondary lymphoid nodule was comprised of 4 areas: follicle-associated epithelium (FAE), dome area (DA), follicular area (FA) and parafollicular area (PFA). The tubal tonsil and the tonsil of the soft palate were macroscopically visible after fixation in 2% acetic acid. These tonsils consisted of scattered lymph nodules, aggregations of lymphocytes and diffuse lymphoid tissue. Because of closely adjacent anatomical position, the palatine tonsil and the paraepiglottic tonsil were lined with stratifed squamous epithelium. The pharyngeal tonsil and the tubal tonsil were lined with pseudostratifed columnar ciliated epithelium. The epithelium covering the tonsils and their crypts was frequently infltrated heavily by lymphocytes. The palatine tonsil possessed a large number of obvious crypts which increased the epithelial surface area potentially exposed to antigen. The surface of the soft palate were lined with stratifed squamous slightly keratinised epithelium. The lingual tonsil could not be located by any macroscopic landmarks, even with fixation in 2% acetic acid. The lingual tonsil was consisted of small aggregations of lymphocytes. The results indicates that 6 tonsils in the adult bactrian camel have the cytologic basis of normal mucosa reaction, which may play a major role in immune responses.