Histology and Innervation of Facies Inferior Linguae in Goat

Abstract

The marginal parts of the facies inferior linguae of goat are covered by a thick epithelium as is the dorsum linguae and contain low filiform papillae and relatively well-developed fungiform papillae, the latter being provided with taste-buds and denser in distribution than on the dorsum of the tongue.
The posterior part of the facies inferior linguae, except the lateral margins, is covered by a smooth surfaced mucous membrane with a thin non-cornified stratified flat epithelium and is devoid of tongue papillae standing out from the surface, but small papillae are sent out from the propria into the epithelium.
The transitional zone from the facies inferior linguae into the oral cavity base, especially the facies inferolateralis linguae, is covered by a rather thick non-cornified epithelium, and here the papillae growing out of the propria is relatively welldeveloped. A small number of filiform papillae are also found in formation here.
In the transitional zone between the facies inferolateralis linguae and the oral cavity base is formed a conspicuous longitudinal ridge and a single row of several tongue papillae, very tall in height and provided with a horn-plate, is standing on it. These papillae, though peculiarly shaped, are probably nothing but filiform papillae of unique type in essence.
The sensory fibres supplied to the filiform papillae in the marginal parts of the facies inferior linguae of goat are very small in number, corresponding to the poor development of the connective tissue papillary stocks. Their terminations are found very simply, being found only a small number of unbranched and very simple branched terminations. But the well-developed fungiform papillae are rich in sensory innervation. The sensory fibres are numerous and rather complex branched terminations are found here. Especially, close beneath the taste-buds, plexus-like sensory terminations are often found. A part of the terminal fibres pass over into intraepithelial fibres. Some intra- and extra-gemmal fibres are found in the tastebuds.
The smooth-surfaced mucous membrane of the posterior part of the facies inferior linguae and the facies inferolateralis are poor in sensory innervation, the terminations comprising only the unbranched and the very simple branched types in most cases. In the peculiar long tongue papillae above, however, the sensory fibres are more numerous, and beside the unbranched and branched terminations, we found not rarely some intraepithelial fibres in them.
Beside the above-specified sensory terminations, some peculiar end-bulbs are also in existence in the propria mucosae of the facies inferior linguae. The end-bulb is of club-like form encased in a thin connective tissue capsule, its inner bulb consists of a light outer zone and a darkish inner zone rich in special cell nuclei. A single sensory fibre runs into the inner zone and ends after slowly swelling out into club-form. These end-bodies are found not only in the propria of the inferior surface but also of the inferolateral surface and of the dorsum of the tongue, and besides, are found in the fungiform papillae and the peculiar long tongue papillae, too.