Figure 4

The pharyngeal fold and caudo-lateral extension with enclosed pharyngeal tonsil in D. novaehollandiae. a-c: Progressively more lateral longitudinal sections as indicated by the dotted line in the inset. Note the numerous simple, branched, tubular mucus-secreting glands (Gl) and associated lymph nodules (*) and inter-nodular lymphoid tissue surrounded by connective tissue (Ct) present on the ventral surface of the pharyngeal fold (Pfv). The follicular pharyngeal tonsil (Ft) is formed by a large number of lymph nodules and inter-nodular (Ilt) lymphoid tissue enclosed between the dorsal surface of the pharyngeal fold (Pfd) and the ventral surface of the extension (P). The extension is supported by a core of connective tissue (Ctc). The dorsal surface of the extension contains simple, tubular mucus-secreting glands (Sg). Note the long crypt (dotted arrow) which branches. Non-follicular tonsil (Nft). The recess between the dorsal surface of the pharyngeal fold and proximal esophagus (not on figure) is indicated (R). c: Longitudinal section near the lateral edge of the extension showing the well-encapsulated lymphoid tissue surrounded by connective tissue and the branching of the tonsillar crypts. Lymphonoduli pharyngeales (Lp) are associated with the glands but not situated directly below the epithelium. Inset: Caudo-lateral extension (star).