Ultrastructure and histochemistry of human anterior lingual salivary glands (glands of Blandin and Nuhn).

BACKGROUND

Specimens of human anterior lingual salivary glands obtained by surgery and by dissection of cadavers were studied ultrastructurally and histochemically.

METHODS

Specimens were obtained by surgery for ultrastructural study. Other specimens for histochemistry were obtained by dissection of fresh cadavers. Tissues for electron microscopy were fixed and processed by conventional means. Formalin-fixed cadaver specimens were subjected to a battery of tests for glycoconjugates.

RESULTS

The anterior lingual salivary glands are composed predominantly of mucous tubules (which come in two distinct sizes: large and small), seromucous demilunes, and rare seromucous acini. Regardless of tubule size, mucous cells are typical in appearance and, like mucous cells in other human salivary glands, contain filamentous bodies. Histochemically, the larger tubules contain neutral glycoproteins, low concentrations of sialoglycoproteins, and large amounts of sulfated glycoproteins. The small mucous tubules contain neutral glycoproteins, much sialoglycoprotein, and relatively small amounts of sulfated glycoprotein. The seromucous cells, whether demilunar or acinar, are identical. They contain numerous secretory granules, which show a spectrum of internal patterns from one individual to another. These cells have considerable concentrations of neutral- and sialoglycoproteins and lower concentrations of sulfated glycoproteins. Contrary to previously published reports, we could find no differences in the ratio of mucous to seromucous cells along the anterior-posterior lingual axis: there was no gradient of seromucous cells in our specimens. The ducts in the anterior lingual salivary glands are not precise counterparts of those in the major salivary glands, since the former have no capsules, hence lack lobulation. Without these familiar structural landmarks, the only duct that can be identified with certainty is the intercalated duct, and then only if it is in continuity with or lies close to a secretory endpiece. Such ducts consist of simple cuboidal epithelium of prosaic appearance. The ductular epithelium gradually thickens and gives rise to what appear to be excretory ducts consisting of columnar cells with few mitochondria. Scattered within the walls of the larger ducts are patches of typical striated ducts wherein the taller cells display basal striations resulting from highly folded basal plasma membranes and numerous, vertically oriented, virgulate mitochondria. In other atypical regions of the excretory duct, basal cells may have a primary cilium that juts into the intercellular space.

CONCLUSIONS

There is a high degree of structural variability in human anterior lingual salivary glands. Because of the technical difficulties in collecting pristine saliva from these glands, the precise function(s) of these organs remains unknown.