Distribution of taste buds on fungiform and circumvallate papillae of bovine tongue

The distribution of taste buds on the fungiform and circumvallate papillae of the cow tongue has been determined. The two tongues studied were from Holstein-Friesian cows four to six years of age; they contained 14,765 and 21,691 taste buds, respectively. The tip of the tongue is well supplied with fungiform papillae, and the posterior portion contains the circumvallate papillae. The midportion of the tongue contains relatively few taste papillae. The fungiform papillae contained 1,580 and 1,838 taste buds on the two tongues, respectively, and the circumvallate papillae were estimated to contain 13,185 and 19,853 taste buds. The highest concentration of taste buds therefore occurs in the circumvallate papillae; these relatively few papillae contain approximately 90% of the taste buds. On a circumvallate papilla, taste buds are found only on the papillary sidewall, with none either on the apical surface of the papilla or on the outer wall of the moat.     

Light and scanning electron microscopic study on the lingual papillae and their connective tissue cores of the Cape hyrax Procavia capensis

We examined the epithelial surface and connective tissue cores (CTCs) of each lingual papilla on the Paenungulata, Cape hyrax (Procavia capensis), by scanning electron microscopy and light microscopy. The tongue consisted of a lingual apex, lingual body and lingual root. Filiform, fungiform and foliate papillae were observed on the dorsal surface of the tongue; however, fungiform papillae were quite diminished on the lingual prominence. Moreover, no clearly distinguishable vallate papillae were found on the tongue. Instead of vallate papillae, numerous dome-like large fungiform papillae were arranged in a row just in front of the rather large foliate papillae. Foliate papillae were situated in the one-third postero-lateral margin of the lingual body. The epithelium of filiform papillae was covered by a keratinized layer with kerato-hyaline granules, whereas weak keratinization was observed on the interpapillary epithelium. The external surface of the filiform papillae was conical in shape. CTCs of the filiform papillae were seen as a hood-like core with a semicircular concavity in the anterior portion of each core. Large filiform papillae were distributed on the lingual prominence. The CTCs of large filiform papillae after exfoliation of their epithelium consisted of a concave primary core and were associated with several small protrusions. The surface of fungiform papillae was smooth and dome-like. After removal of the epithelium, CTCs appeared as a flower bud-like primary core and were associated with several protrusions that were arranged on the rim of the primary core. Several taste buds were found on the top of the dorsal part of the epithelium of both fungiform and large fungiform papillae. Well-developed foliate papillae were seen and numerous taste buds could be observed in the lateral wall of the epithelium in a slit-like groove. The morphological characteristics of the tongue of the Cape hyrax had similarities with other Paenungulata such as Sirenia. However, three-dimensional characteristics, especially CTCs of lingual papillae, exhibited multiple similarities with rodents, insectivores and artiodactyls.     

Morphology of the lingual papillae and their connective tissue cores in the cape hyrax

The dorsal lingual surfaces of four adult cape hyraxes (Procavia capensis) were examined by scanning electron microscopy (SEM). Filiform, fungiform and foliate papillae were observed. The lingual body had lingual torus on the posterior third. In the lateral sides of the tongue large fungiform papillae were observed and in the lateral sides of the torus very developmental foliate papillae were observed. Many fungiform papillae were observed in the ventral surface of the lingual apex. No vallate papillae were seen on the dorsal surface. The filiform papilla on the apical surface of the tongue had shovel-shaped papilla. The filiform papilla contained the connective tissue core consisting of some processes. The connective tissue core of the fungiform papillae was floral bud in shape. In the surface of the lingual torus numerous dome-shaped papillae are found. The dome-shaped papilla contained the connective tissue core consisting of a zigzag surface structure and the connective tissue core is surrounded by the processes of various sizes. In the surface of the lingual root numerous openings of the lingual glands were found. Around the glandular openings connective tissue ridges formed circular sheaths. In the lateral sides of the tongue large fungiform papillae were round in shape. The connective tissue core of the fungiform papilla was floral bud in shape. The foliate papillae were seen on the dorsolateral aspect of the tongue and some ridges and grooves were exposed reciprocally. Many small protrusions appeared on the connective tissue core of the ridge of the foliate papilla. These findings suggested that in the structure of the lingual papillae of the cape hyrax there was intermediate type between Rodentia and Artiodactyla.     

NaCl thresholds: relationship to anterior tongue locus, area of stimulation, and number of fungiform papillae

NaCl detection thresholds were determined for 12.5- and 50-mm(2) lingual areas at four anterior tongue locations in eight subjects using a device that allowed for accurate temporal and spatial presentation of tastants to small regions of the anterior tongue. The locations, all on the right side of the tongue, were the tongue tip, an area 1.7 cm posterior to the tongue tip, and regions 1.7 and 3.4 cm posterior to the tip along the tongue's lateral margin. Stimulus duration was 0.75 s. Thresholds were established using a two-alternative forced-choice single-staircase procedure, and the number of fungiform papillae at each stimulation site was counted with the aid of videomicroscopy. NaCl thresholds were lower for the 50-mm(2) than the 12.5-mm(2) stimulation area at all target sites, and were directly related to papillary number among and within the stimulated regions. For a given number of papillae, thresholds were lower within the 12.5-mm(2) than within the 50-mm(2) stimulation region, likely reflecting taste bud density and activation of common afferent pathways. The tongue tip was more sensitive than any other tongue region, and the lateral margins were seemingly more sensitive than the lingual centrum. Large individual differences in taste sensitivity and tongue papilla numbers were noted, and some subjects were insensitive to the highest tastant concentrations at the nontip loci. This study empirically demonstrates that NaCl detection sensitivity varies across discrete regions of the anterior tongue and is related to the relative number and density of fungiform papillae.     

Comparative morphological study on the lingual papillae and their connective tissue cores (CTC) in reeves’ muntjac deer (Muntiacus reevesi)

The lingual papillae and their connective tissue cores (CTC) from Reeves’ muntjac deers (herbivorous artiodactyla) were studied using light and scanning electron microscopy and then compared to those of other mammalian species. At the posterior portion of the tongue, the Reeves’ muntjac has a lingual prominence on which large conical papillae are distributed. On the dorsal surface of the anterior tongue, numerous filiform papillae were found. Externally, each filiform papilla consists of a rod-shaped main process and several small accessory processes. Their CTCs consist of 10 or more rod-shaped processes arranged in a horseshoe pattern and several posterior processes forming a small circular pattern. This structure is a common characteristic of artiodactyla, through which Reeves’ muntjac deer can be categorized in a position in the artiodactyla class lying between the bighorn sheep and the East African bongo. Fungiform papillae are distributed among the filiform papillae on the anterior portion of the tongue. Large fungiform papillae are also sparsely distributed on the lingual prominence and have several taste buds in the epithelium on the surface. Ten or more vallate papillae are distributed at the postero-lateral area of the lingual prominence and numerous taste buds are distributed in the epithelium of their side.     

Light and Scanning Electron Microscopic Study on the Structure of the Lingual Papillae of the Feathertail Glider (Acrobates pygmeus,Burramyidae, Marsupialia)

The structure of the tongue of the marsupial feathertail glider (Acrobates pygmeus) was observed under a light and scanning electron microscope. The elongated tongue with a sharpened apex is ca. 10 mm in length. Only the posterior half of the tongue is attached to the bottom of the oral cavity by the frenulum, which facilitates considerable mobility of the anterior free part of the tongue. On the dorsal surface of the tongue, three types of lingual papillae were distinguished, that is, mechanical filiform papillae and gustatory fungiform and vallate papillae. The arrangement, shape, and size of filiform papillae and the direction of their keratinized processes change depending on the part of the tongue, so that the surface of the apex and the body of the tongue resembles a brush adapted to effective holding of semiliquid food and collection of pollen. The fungiform papillae have a single taste bud and are uniformly scattered between filiform papillae only on the anterior half of the tongue. On the smooth root of the tongue, three oval vallate papillae are arranged in the form of a triangle, similarly as it is the case in other marsupials. The posterior biggest vallate papilla is oriented perpendicularly to the smaller anterior papillae. The results of the study on the feathertail glider show that the special arrangement of lingual papillae is strongly adapted to feeding behavior of this nectar‐eating and frugivorous animal. Anat Rec, 290:1355–1365, 2007. © 2007 Wiley‐Liss, Inc.     

Development of fungiform papillae: patterned lingual gustatory organs

The fungiform papilla is a gustatory organ that provides a specific tissue residence for taste buds on the anterior tongue. Thus, during development there must be a progressive differentiation to acquire papilla epithelium, then taste cell progenitor epithelium, and finally taste cells within the papilla apex. Arranged in rows, the patterned distribution of fungiform papillae requires molecular regulation not only to induce papillae, but also to suppress papilla formation in the between-papilla tissue. Intact sensory innervation is not required to initiate papilla development or pattern. However, members of several molecular families have now been identified with specific localization in developing papillae. These may participate in papilla development and pattern formation, and subsequently in taste progenitor and taste cell differentiation. This review focuses on development of fungiform papillae in embryonic rat and mouse. Basic morphology, cell biology and molecular phenotypes of developing papillae are reviewed. Regulatory roles for molecules in several families are presented, and a broad schema is proposed for progressive epithelial differentiation to form taste cell progenitors in parallel with the temporal course, and participation of lingual sensory innervation.     

Scanning electron microscopy study of the tongue and lingual papillae of the California sea lion (Zalophus californianus californianus)

We observed the three-dimensional structures on the external surface and the connective tissue cores (CTCs) of the California sea lion (Zalophus californianus californianus), after exfoliation of the epithelium of the lingual papillae (filiform, fungiform, and vallate papillae), using scanning electron microscopy (SEM) and conventional light microscopy. Macroscopically, the tongue was V-shaped and its apex was rounded. At the posterior area of the tongue, five vallate papillae were arranged in a V shape. In the epithelium, numerous taste buds were distributed on the top of the vallate papillae. On the dorsal surface from the apex to the boundary between the anterior and posterior tongue, filiform papillae were densely distributed. The CTCs of the filiform papillae consisted of a main protrusion (primary core) and many small cores (secondary cores). From the apex to the anterior one-third of the tongue, dome-like fungiform papillae were densely distributed, whereas fewer were located at the posterior two-thirds of the tongue. Several taste buds were found in the epithelium on the fungiform papillae. The size of the filiform papillae gradually increased from the apex to the boundary between the anterior and posterior tongue. At the lingual radix, the conical papillae, which were bigger than any filiform papillae, were densely distributed. The morphological characteristics of the tongue of the California sea lion appear to have been transformed to adapt to an aquatic environment; however, they possess some structures similar to those of land mammals.     

Morphology of the lingual papillae in the raccoon dog and fox

The dorsal lingual surfaces of the raccoon dogs (Nyctereutes procyonoides) and fox (Vulpes vulpes japonica) were examined by scanning electron microscopical (SEM) observations. The distribution and type of the lingual papillae found in the raccoon dog were similar to those in the fox. Filiform, fungiform, foliate and vallate papillae were observed. The filiform papillae were distributed over the entire dosal surface of the tongue. Each filiform papilla on the apical surface of the tongue had several pointed processes. The filiform papillae of the lingual body consisted of a main papilla and some secondary papillae. The fungiform papillae were present rounded bodies, and more densely distributed on the lingual apex. The foliate papillae were seen on the dorsolateral aspect of the tongue. The vallate papillae were located on both sides of the posterior end of the lingual body. Each papilla was surrounded by groove and crescent pad. On the periphery of the papillae, large conical papillae were observed.     

The nature of the substance P-containing nerve fibres in taste papillae of the rat tongue

The nature of the association of substance P (SP) with taste buds in the rat tongue was investigated by immunohistochemical and radioimmunoassay techniques. Both the circumvallate and fungiform papillae were found to receive a rich innervation by substance P-containing fibres. Although these fibres were closely associated with the taste buds in these structures, they assumed a perigemmal rather than an intragemmal location. Bilateral lesions of the glossopharyngeal nerve resulted in the depletion of taste buds from the vallate papilla and a large reduction in substance P immunoreactive fibres in this area. Lesions of the chorda tympani, which led to the degeneration of taste buds in fungiform papillae, had no effect on the immunohistochemical appearance of substance P in these papilla or on the substance P levels in the anterior part of the tongue. Lesions of the mandibular division of the trigeminal nerve or neonatal capsaicin treatment had no effect on the structural integrity of taste buds in fungiform papillae but led to the depletion of substance P-immunoreactive fibres from these papillae. Both of these procedures caused a 71% reduction in the substance P content of the anterior tongue, ipsilaterally after the nerve lesion and bilaterally after capsaicin treatment. The results are discussed in relation to the possible functional role of substance P-containing fibres within nerves supplying taste structures of the tongue.     

Scanning electron microscopic study on the tongue and lingual papillae of the adult Spotted seal, Phoca largha

We observed the external surface and connective tissue cores (CTCs) of the lingual papillae (filiform, fungiform and vallate papillae) of adult Spotted seals (Phoca largha) using SEM and light microscopy. The tongue was V-shaped and its apex was rather rounded. On the dorsal surface from apex to the one-third posterior of the tongue, the lingual mucosa was densely covered by filiform papillae, with a scatted distribution of dome-like fungiform papillae, which have orthokeratinized epithelium. At the posterior part of the tongue, filiform papillae were totally diminished and their epithelium was parakeratinized. Approximately 6-7 vallate papillae were arranged in a V-shape on the posterior of the tongue. After removal of the epithelium, the CTCs of the filiform papillae that were distributed at apex consisted of a primary core and approximately 5-6 rod-shaped small accessory cores. The CTCs of filiform papillae that were distributed at anterior part of the tongue lacked primary protrusions and possessed approximately 10-15 rod shaped small accessory cores that were arranged in a horseshoe manner. The CTCs offungiform papillae had cylindrical primary cores and were fringed with accessory protrusion. In the Vallate papillae, taste buds were only seen at the dorsal epithelium.     

Morphology of the lingual papillae in the tiger

The dorsal lingual surfaces of an adult tiger (Panthera tigris altaica) was examined by macroscopical and scanning electron microscopical observations. Filiform, fungiform and vallate papillae were observed. The filiform papillae were distributed over the entire dosal surface of the tongue. The fungiform papillae were present rounded bodies, and more densely distributed on the lingual apex. There were 4 vallate papillae in total on borderline between the lingual body and lingual radix. Each papilla was surrounded by a groove. No foliate papillae were seen on the dorsal surface. Openings of the glandular ducts on the regions of the vallate papillae were found.     

Quantitative study of fungiform papillae and taste buds on the cat's tongue

The number of fungiform papillae has been counted on the tongues of six adult cats and of kittens both at birth and aged 2 and 4 months. Papillae were sampled from different regions of the tongue, and their size and the number of taste buds they contained were determined using histological sections taken parallel to the tongue surface. There were approximately 250 fungiform papillae on the tongues of the adult cats, the papillae were most numerous at the tip of the tongue, and there was no significant difference between the number of papillae on each side. The size of the papillae increased from a mean maximum diameter of 0.28 mm at the tip of the tongue to 0.48 mm at the back; the mean number of taste buds increased correspondingly from 6.9 to 16.6. The kitten tongues had a number and distribution of fungiform papillae similar to that found in the adults. In the neonate, papillae were smaller and contained fewer taste buds; these parameters increased with the corresponding increase in tongue size in the 2- and 4-month-old kittens.     

Three-dimensional architecture of the connective tissue papillae of the mouse tongue as viewed by scanning electron microscopy

The morphological relationship between lingual papillae and underlying connective tissue papillae of mouse was studied because it is conceivable that the differentiation of epithelium may be affected by its connective tissue. Tongues of adult male mice were fixed in formol or Karnovsky's fixative. After removal of the epithelium by long-term hydrochloric acid treatment at room temperature, the surface of the connective tissue papillae was observed by scanning electron microscopy. Connective tissue papillae that were fungiform in shape and which were distributed at the anterior part of the tongue showed barnacle-like protrusion after removal of the epithelium. Their surface was covered by numerous long filaments running vertically and there was a round depression on the top of each fungiform papilla that may be found to correspond to a taste bud when the results of light and electron microscopy are compared. Filiform papillae in a narrow sense were closely distributed in the anterior part of the tongue. They had a tapered tip declining posteriorly. Each filiform connective tissue papilla was conical in shape and had a round depression that slightly declined antero-downward, and a long narrow depression ran along the anterior edge of each connective tissue papilla. Large conical papillae which distributed at the anterior margin of the intermolar prominence had shovel-like connective tissue papillae which had a depression at the posterior surface unlike that of the filiform papillae. Branched papillae distributed in the posterior part of the prominence had a depression at the anterior surface. Under the light microscope, numerous keratohyaline granules were seen to be contained only in the posterior epithelial cell line of the large conical papillae distributed in the anterior margin of the prominence, while these granules were found only in the anterior epithelial cell line of both filiform and branched papillae. It became clear that the axes of each connective tissue papilla of large conical papillae distributed radically around a single midpoint. Connective tissue papillae of vallate papillae had a beehive-like shape and in follicate papillae there were several vertical elliptical gaps, seen when the epithelium was peeled from the connective tissue.     

Comparative morphological study on the lingual papillae and their connective tissue cores in rabbits

The morphological structure of the lingual papillae and their connective tissue cores (CTC) in a rabbit were studied using LM and SEM and were compared to that of other animal species. Externally, the filiform papillae distributed on the anterior surface of the dorsal tongue were short and conical with a round base and had a flat area on their anterior upper half. The CTC of the conical filiform papillae had a roughly triangular plate-like structure with a round top. Several small round protrusions were found on both inclined planes of the triangle. Spearhead-like filiform papillae were distributed on the anterior edge of the lingual prominence and branched filiform papillae were on the posteriorly wide area of the prominence. These papillae on the prominence had a slightly ramified CTC that differed from that of the CTC of the conical filiform papillae distributed on the anterior tongue. Dome-like fungiform papillae were distributed among the conical filiform papillae of the anterior tongue and had a CTC with a roundish structure that was almost but, not quite spherical in appearance with 1 to 10 small round concave indentations for taste buds on their upper surface. The foliate papillae had approximately 15 parallel ridges separated by grooves. These ridges contained a parallel thin plate-like CTC exhibited after removal of the epithelium. The vallate papilla was comprised of a spherical central papilla and had a circular wall with a flower-like CTC almost resembling a carnation. The stereostructure of the rabbit's filiform CTC are comparatively described as being morphologically in between those of rodents and those of the guinea pig and Japanese serow. Such evolution has probably occurred due to the species unique masticatory and gustatory needs and functions.     

Morphology of the lingual papillae in the Patagonian cavy

We examined the dorsal lingual surfaces of an adult Patagonian cavy (Dolichotis patagonum) by scanning electron microscopy. The tongue of the Patagonian cavy is about 8 cm long and the lingual body had lingual prominence on the posterior third. There were no fungiform papillae in the lingual dorsal surface. The fungiform papillae were observed in both lateral sides of the lingual apex. The filiform papilla of the lingual body consisted of a large conical papilla. The connective tissue core of the filiform papilla showed many slender processes. The fungiform papillae were round in shape. The connective tissue core of the fungiform papilla was flower-bud shaped. Two vallate papillae were located on between lingual body and root, and insert in two grooves. The connective tissue core of the vallate papilla was covered with numerous small spines. Many foliate papillae were observed on the posterolateral regions of the tongue. After removing epithelium from the foliate papillae many vertical depressions became apparent. These findings suggest that in the structure of the lingual papillae of the Patagonian cavy there is similar to that of the capybara.     

Morphology of the lingual papillae in the Japanese marten

The dorsal lingual surfaces of two adult Japanese marten (Martes melampus) were examined by scanning electron microscopy (SEM). Filiform, fungiform, vallate and foliate papillae were observed. A small filiform papilla on the apical surface of the tongue had several pointed processes. A small filiform papilla contained the connective tissue core consisting of several small processes. A large filiform papilla of the lingual body consisted of a main papilla and some secondary papillae. A large filiform papilla contained the connective tissue core consisting of processes of various size. The fungiform papillae are round in shape. The connective tissue core of the fungiform papilla had a top with several round depressions. The four vallate papillae were located on both sides of the posterior end of the lingual body and each papilla was surrounded by groove and crescent pad. A zigzag surface structure appeared on the connective tissue core of the vallate papilla. The foliate papillae were seen on the dorsolateral aspect of the tongue and some ridges and grooves were exposed reciprocally. A zigzag surface structures appeared on the connective tissue cores of the ridges of the foliate papillae.     

Morphological characteristics of the tongue and lingual papillae of the large bamboo rat (<Emphasis Type="Italic">Rhizomys sumatrensis</Emphasis>)

The large bamboo rat (Rhizomys sumatrensis) is a fossorial rodent found throughout Indochina that has a distinct habitat dominated by bamboo thickets. In the study reported here, the lingual biology of this rodent is described in detail, based on characteristic features of the tongue and lingual papillae as determined by light and scanning electron microscopy studies. The tongue was found to be elongated with a rounded apex and possessed a median groove and a well-developed intermolar prominence. Three types of the papillae were found on the dorsal lingual surface: filiform, fungiform and vallate papillae. The most abundant papillae were the filiform papillae, the majority of which had a wide base and fork-like processes. Rounded fungiform papillae with one to four taste buds were randomly distributed among the filiform papillae, with a high density found at the anterior tongue, particularly the apex. Two oval vallate papillae were observed on the posterior part of the tongue, surrounded by a circumferential groove into which their numerous gustatory pores opened. The lingual radix had no papillae but contained mucus-secreting Weber’s salivary glands. Structural adaptations of the tongue to meet the functional demands of food ingestion and food manipulation in the oral cavity are also discussed.     

Morphology of the dorsal lingual papillae in the barbary sheep, Ammotragus lervia

The dorsal lingual surface of a barbary sheep (Ammotragus lervia) was examined by scanning electron microscopy (SEM). The tongue was about 20 cm in length. There were about 30 vallate papillae on both sides. Filiform, conical, fungiform and vallate papillae were found. The filiform papillae were distributed over the entire dorsal surface of the tongue, excepted for the lingual torus where conical papillae were present. The fungiform papillae were present rounded bodies, and more densely distributed as compared to that of the lingual body on the tip and ventral surface of lingual apex. No foliate papillae were seen on the dorsal surface. The vallate papillae were located on both sides of the midline in the caudal part. Each papilla was surrounded by a groove. These findings indicate that the tongue of the barbary sheep is similar to that of the formosan serow, japanese serow and blackbuck.