The Morphology And Distribution Study Of Nerve Terminals About Lingual Tactile Of Food

The tongue is an extremely complex multifunctional tissue, which is related to the talking, chewing, swallowing and tasting food. Especially, in the process of perceiving food, tongue is not only used to identify the basic taste (including sour, sweet, bitter, salt and uami), but also to perceive hot, warm and tingle from nongustatory chemicals, as well as distinguish shape, texture and soft degree of the food. On the whole, tongue is a highly developed tactile tissue just like the skin which can feel touch and different frequency vibration by Meissner corpuscle, Mekel cell, Pacinian corpuscle and Ruffini terminal corpuscle in the dermal layer. These corpuscles are all composed of peripheral nerve terminals with and without myelin sheath. Therefore, the hypothesis was advanced that there were mechanoreceptor such as Meissner or Krause corpuscle under the lingual surface. It is aimed to investigate the terminal innervation of fungiform and filiform papillae so as to better understand the functional role of them in contacting food.On the basis of this hypothesis, The morphology and distribution of nerve terminals under the filiform papillae and fungiform papillae were studied by electronic microscope, immunohistochemical, immunofluorescence, silver impregnation, laser confocal scanning microscope and so on. For this research, ICR mouse as experimental animal were used. Meanwhile, human beings as detection subjects, sensory and threshold were completed by gLMS and Semmes-Weinstein monofilament to demonstrate the results from tissue experiment. The results of this study were as follows:(1) The result of histology revealed that tongue, as one of the special tactile receptors, has the terminal neuron-morpha under the papillae similar to that of the dermal skin. It composed of two types of terminals, one is free nerve fibers and another is organized nerve corpuscle. The free nerve fibers were observed in epithelium perigemmal thought to detect the tactile, thermal, nonciception etc. The organized corpuscles which were Krause-like or Meissner-like were found in the anterior and posterior tongue respectively.(2) Fungiform papillae and filiform papillae play the most important role in lingual tactile. The terminal innervations have difference in spatially distribution. From the anterior area to the posterior, the nerve fibers descending from the perigemmal to the apex of connective tissue core of filiform papillae while the special organized nerve terminals ascending into the connective tissue core from the muscle layer. The quantitative analysis has indicated that the special nerve corpuscles located much more than that of the anterior.(3) The result of sensory testing showed that fungiform papillae have the more tactile acuity than the filiform papillae. It indicated that nerve fibers have the higher sensitivity than that of organized corpuscle due to the different mechanical transduction. In addition, the fact that threshold of filiform papillae as same that ring finger has also demonstrated that the terminal corpuscle within the filiform papillae on the posterior was Meissner corpuscle. It function as a mechanoreceptor for food shape and textureIn conclusion, the result above has revealed that fungiform and filiform papillae play important role in the process of contacting, tasting and swallowing food, and provide an valid evidence for the chosen and preference for food.