Innervation especially Sensory Innervation of Facies Inferior Linguae in Human Adult

Abstract

The epithelium of facies inferior linguae mostly is much thinner than that of dorsum linguae, the formation of the papillae being correspondingly weaker, especially as the rear parts are approached. But, in the marginal parts the epithelium is thicker, and large papillae provided with secondary papillae or especially with taste-buds are observable accordingly. As the epithelium of the vicinity of.the median line is thick too, comparatively large papillae or taste-buds.papillae can be seen also here. However, all of the papillae seen in facies inferior linguae even do not admit protrusion of epithelium over the surface, in contradistinction to the papillae in dorsum linguae, and the epithelial surface is kept always smooth and even. The epithelium of the plica fimbraiata is thinnest and the papillae are of poorest development, vet a very few of small taste-buds are provable.
The plexus formed in the subepithelial layer consists of thick sensory and fine vegetative fibres, the latter finally passing into the Stohr's terminalreticulum. The sensory fibres are of much weaker development than in dorsum linguae, but are rather well-developed in accordance with the development of the papillae. So, the development of sensory terminations in marginal parts and the vicinity of the median line is considerable.
The sensory terminations in facies inferior linguae may be divided into simple unbranched and branched terminations, complex branched terminations, non-capsulated and capsulated glomerular terminations, and special terminations for taste-buds.
Of the sensory terminations found in the large papillae without tastebuds, glomerular terminations, especially capsulated ones, and plexuslike terminations may be mentioned as of special interest, though they are much lower numerically than in dorsum linguae. The former consist of thick sensory fibres, which after losing the myelin, show peculiar change in size and a winding course and terminate in simple glomerular arrangement. They are in general capsulated and provided with numerous special nuclei in the inner bulb. Plexus-like terminations are composed of two or three thick sensory fibres dividing into two or three branches, which show the irregular plexus-like terminal arrangement.
The development of sensory fibres for the samil papillae is very weak in comparison with the above, and many of them even lack sensory fibres. And in small papillae where sensory fibres enter, their terminal mode is simple, mostly represented by unbranched or simple branched terminations. However, there are found not rarely corpusclar, especially simple noncapsulated glomerular terminations, and two or three such bodies can be found in one small papilla, though in a small quantity.
In the large taste-bud papillae, plexus is formed at the base, and the sensory fibres penetrate the papillae, being accompanied by vegetative fibres, mostly to pass into simple arborized or undetermined terminations, but partly into corpusclar, especially into non-capsulated glomerular terminations. These bodies are frequently formed just beneath the tastebuds, sometimes sending out intra- and extragemmal fibres.
The small taste-bud papillae are very often devoid of sensory fibres, but sometimes sensory fibres run into them with vegetative fibres, to pass into non-capsulated glomerular terminations in the tip of the papillae, more rarely sending out intragernmal fibres.
As detailed above, since the morphological development of sensory fibres for the taste-buds found in facies inferior linguae is incomparably weaker than in the papillae circumvallatae, it may be assumed that they are also functionally much degenerated ones.