Morphological study of the sensory innervation of the rat labial mucosa

The sensory innervation of the rat labial mucosa was investigated by means of methylene blue vital staining and osmic acid staining. Sensory receptors in this region were of three kinds (free nerve endings, encapsulated corpuscles and bush-like nerve endings) which constituted separate sensory units respectively. The encapsulated corpuscles were observed in the deep part of lamina propria, and distributed mainly in the margin of labial mucosa. Almost all (78.8%) of encapsulated corpuscles were of a simple type which had a non-branched axon terminal. No clew-like type corpuscles or glomerular-Meissner corpuscles were observed. The bush-like nerve endings were located in the lamina propria close to the epithelium, and localized in the central part of labial mucosa where the formation of papillae was remarkable. The density of the encapsulated corpuscles in the entire mucosa was 3.5-5.3/mm2, and that of the bush-like nerve endings in the densely distributed area was 38.9-60.6/mm2.