A scanning electron microscopic study of the dorsal surface of the human tongue

To study the dorsal surface of the human tongue using a scanning electron microscopy (SEM), tissue specimens were taken from the anterior part of the tongues of 15 individuals aged from 21- to 28-years-old. The formalin-fixed samples were processed routinely for SEM. With SEM the surface of the normal tongue mucosa was shown to be rather evenly covered by filiform papillae, with some fungiform papillae scattered among them. Filiform papillae consisted of two parts: the body and hairs. The mucosal surface of the body was smooth; the squamous epithelial cells were polygonal, and their boundaries were prominent. On the surface of the superficial epithelial cells were parallel or branching microplicae. Each filiform papilla had 6-10 hairs, which were scaled and covered by an extensive plaque of microorganism. The upper surface of the fungiform papillae was smooth; only a few desquamating cells were seen. The superficial cells had a pitted appearance and cell boundaries overlapped. Taste pores, up to 3 pores in a single papilla, were found on the upper surface. Desquamation was more pronounced on the base of the fungiform papillae than on the upper surface. In almost all fungiform papillae some hairs protruded from the base. Parallel microplicae were found on the surface of the superficial cells of the base. The structure and function of the human tongue, as well as the microplicae of its superficial cells, are compared to those of various species of animals.     

Morphology, and muscle- and papilla-volume ratios, of the tongue of Laudakia stellio (Agamidae, Squamata): a histological and stereological study

We examined the histological structure of the tongue of Laudakia stellio, the starred agama lizard (Agamidae, Squamata), under light microscopy. We also investigated the muscle and papilla volume ratios, with volumes of each aspect of interest estimated according to the Cavalieri method. The macroscopically short, thick and muscle-rich front tip of the tongue of L. stellio does not show any bifurcation, and under light microscopy, the oval-shaped papilla-free front tip was seen to be covered by keratinized stratified epithelium. The dorsal and ventral parts were different, with the former partially covered by keratinized stratified epithelium and rich in secretory glands and secretory cells. The ventral part, which contained keratinized stratified cells, had a flat surface with no papillae. The dorsal surface of the anterior and posterior parts contained fungiform papillae, with the apical parts of these papillae containing minimal keratin; the interpapillar space was covered by keratin-free squamous stratified epithelium. The middle section of the tongue contained cylindrical-type papillae, with serous and mucous secretory glands and ducts at their base. Finally, the frontal and middle parts of the ventral and dorsal surfaces did not contain any taste buds, although there were some in the hind part of the dorsal surface. As morphometric estimates of volumes of the muscles and papillae, the mean volume ratios (relative to total tongue volume)+/-standard deviation were 0.66+/-0.03 and 0.33+/-0.03, with mean coefficients of error of 0.02 and 0.03, respectively.     

Scanning electron microscopy of developing papillae on the tongue of human embryos and fetuses

The appearance and differentiation of papillae on dorsal andlateral surfaces of human embryonic and fetal tongues, at variousdevelopmental ages, were studied by scanning electron microscopy.Formaldehyde and phosphate buffer fixation provided satisfactorypreservation. At 8–9 weeks, the anterior two-thirds ofthe tongue showed no obvious signs of papillae. In contrast,just anterior to the sulcus terminalis rounded elevations wereseen, suggesting initial signs of circumvallate papillae. At10–13 weeks, the distribution and shape of elevationson the anterior two-thirds of the tongue indicated the beginningof fungiform papillae. Openings located on the dorsal surfaceof many of these fungiforms contained an amorphous central structureprojecting out of the papilla. First signs of foliate papillaewere seen at 10 weeks. At 15–18 weeks, fungiform and filiformpapillae were recognized, although sometimes their borders wereobscured by scaling epithelial cells. At 23–26 weeks,all papillae exhibited their adult form. ^*Presented, in part, at the VIth International Symposium onOlfaction and Taste, Gif-sur-Yvette, Paris, France, 15–17thJuly, 1977.     

Visualizing Taste Papillae In Vivo with Scanning Electron Microscopy of a High Resolution Cast

A method using polyvinylsiloxane (PVS), a high-resolution dentalimpression material, to obtain negative images of lingual surfacesis described. Epoxy-resin tongue replicas made from these impressionswere examined with scanning electron microscopy (SEM). Thismethod has been developed to visualize structural details ofthe tongue surface of living human beings and laboratory animals.The utility of the method is demonstrated with hamster tongues,which have well-defined fungiform papillae with single tastepores, and human tongues, which have more variable surface structures.Replicas made from PVS impressions of tongues of living hamsterswere compared with the same tongues after fixation. The replicascontained much of the detail present in fixed tongues. WithSEM, it was possible to identify individual fungiform papillae,which contained depressions with the size and the location ofhamster taste pores. Individual papillae could also be recognizedin human-tongue replicas, but taste pores could not be identifiedwith certainty. These replicas provide permanent, three-dimensionalrecords of tongue topography that could be used to documentchanges due to trauma, disease and aging.     

Argentophilic and scanning electron microscopic observations of the tegumentary papillae of Echinostoma revolutum (Trematoda) cercariae

Argentophilic staining and scanning electron microscopy (SEM) were used to study the tegumentary papillae of Echinostoma revolutum cercariae. The most abundant papilla was uniciliate and arranged bilaterally on the body and tail of the cercaria. The distribution of these papillae was similar to that seen in other 37-collar spined echinostome cercariae. SEM revealed a total of 18 multiciliate papillae--16 on the anterior end and 2 at the middle of the body. These papillae contained up to 18 cilia per papilla and have not been reported previously from any cercaria.     

Scanning Electron Microscopical Studies of Developing Gustatory Papillae in Humans

Development and morphological changes of human gustatory papillaeduring postovulatory weeks 6–15 have been studied usingscanning and transmission electron microscopy. The first papillaof the tongue appears around postovulatory week 6 in its caudalmidline near the foramen caecum. In contrast, the dorsal epitheliumof the anterior part of the tongue shows only small hillock-or papilla-like elevations from week 6 on, which comprise anaggregation of 5–20 epithelial cells. From week 7 on,most prominent fungiform papillae develop near the median sulcusand at the margins of the anterior part of the tongue. At theirtops, the first primitive taste pores are found around week10; these are often covered with processes of adjacent epithelialcells. Most pores, however, develop around weeks 14–15.The maturation of taste buds does not coincide with the appearanceof taste pores, since taste bud cells are not fully differentiatedin the observed period of time. Fungiform papillae are developedbefore filiform papillae, which do not occur within the first15 weeks of gestation. Fungiform papillae tend to grow betweenweeks 8 and 15 of gestation, whereas the size of vallate papillaeseems to be constant during this period. Chem. Senses 22: 601–612,1997.     

A scanning electron microscope study on the tegument of Proalarioides kobayashii Park, 1940 (Trematoda)

A SEM study was performed on the surface of adult P. kobayashii Park, 1940, recovered from the snake, Elaphe rufodorsata. The anterior part of the worms was cup-shape and equipped with oral, ventral suckers, pseudosuckers, and tribocytic organ, and the posterior one was finger-like and round-ended. The tegument of the anterior body was covered with 3-4 pointed small spines on the mid-ventral surface and 1-2 pointed ones on the lateral surface. Sensory papillae such as type II, dome-shape ones, and papillae with an opening were distributed over the ventral surface of the anterior portion. The round tribocytic organ was bearing small stout spines laterally, whereas the surface which comes in contact with the host tissues consisted of numerous long fibrillar fibers. The lip of the oral sucker contained type II papillae. Lateral margin of the anterior body revealed type III papillae.     

Three-dimensional and surface structures of rat filiform papillae

The three-dimensional and surface structures of the simple conical papillae of the rat tongue have been demonstrated with scanning electron microscopy. The papillary projection was organized into the anterior, posterior and central core cell populations, whereas the basal region of the papilla which consisted of circularly arranged cells showed no differentiation into three autonomic cell populations. It is considered that the anterior and posterior cell populations around the central core tend to be mutually attached at the bilateral sides, and that the posterior and core cell contacts are rather close than the anterior one. The anterior papillary cells showed relatively smooth surface with little micropits and without microridges. The reticular microridges on the basal cell surface of the posterior papillary cells appear to later develop the micropits and linear microridges on the tip cell surface. These suggest that the anterior cell surface is more highly keratinized than the posterior one. The microridges or micropits on the outer cell surface and the microprojections on the inner cell surface organizing filiform papilla are considered to be the structures for the purpose of cell adhesion.     

A note on the hairy achenes of four African species of Scleria Bergius (Cyperaceae)

Surface features of hirsute achenes of four African species of Scleria have been examined by SEM. All bear unicellular, terete hairs with swollen bases. As the achenes mature and dry, the hairs collapse, except for their partly silicified bases, which appear as pit-like depressions from which the now-flattened hairs emerge. If the achene surface is not smooth the hairs are localized on the interlacunar ridges. In addition to the hairs, three of the four species examined show minute papillate protuberances from the silicified outer tangential walls of the epidermal cells. These papillae form a further ornamentation to the achenes visible only at high magnification. The fourth species entirely lacks these papillae.     

Three-dimensional architecture of the connective tissue core and surface structures of the lingual papillae in the rabbit

Three-dimensional characteristics of the epithelial cell layer and connective tissue interface of the tongue were studied using scanning electron microscopy. In this study, the fragments of tongue were fixed in modified Karnovsky's fixative solution. Subsequently, the specimens were treated with 10% NaOH solution for 4-7 days at room temperature and postfixed in 1% OsO4 in 0.1 M phosphate buffer (pH 7.4) for 2 hours at 4 degrees C. They were dehydrated through a graded ethanol series, and critical-point dried with CO2. The specimens were coated with gold and observed in a scanning electron microscope, JEOL JSM-6100. The results showed numerous papillae on the dorsal surface of the tongue divided into four groups (filiform, fungiform, foliate and vallate papillae). Filiform papillae are conically shaped; fungiform papillae have an irregular round surface; foliate papillae are oval in shape and have some parallel projections; and vallate papillae are located in the posterior part of the tongue and have a depression around the center. After the treatment with 10% NaOH solution, the original arrangements of connective papillae could be seen. This characteristic three-dimensional distribution of the collagen fiber bundles is typical for each superficial papillae depending on whether it is filiform, fungiform, foliate or vallate.     

Genomic structure of swine taste receptor family 1 member 3, TAS1R3, and its expression in tissues

Taste receptor family 1 member 3, TAS1R3, is shown to be involved in sweet and umami tastes in mouse, and the nucleotide sequence of the gene has been reported in rat, gorilla, and human. Pigs are frequently used as models for human diseases, and are also considered to be source animals for xenotransplantation to humans due to their anatomical and physiological similarities to humans. Therefore, in the present study, the genomic structure of the swine TAS1R3 gene was determined, and TAS1R3 expression was studied in various swine tissues. The gene was shown to reside on swine chromosome 6q22-->q23, from which three types of mRNAs were generated: 3,752 bp derived from six exons in tongue, 3,704 bp from six exons and 3,630 bp from seven exons in testis. The 6 exons/5 introns were structurally similar to those of humans and mice, but the 7 exons/6 introns structure of TAS1R3 was first observed in swine. High expressions of TAS1R3 were revealed in tongue, kidney, and testis by real-time PCR. The expression profile of the tissues except for kidney was similar to that of mouse. When in situ hybridization using an RNA probe for TAS1R3 was performed on swine tongue and testis tissues, TAS1R3 expressions were revealed in tongue circumvallate papillae, fungiform papillae, mucosal epithelium, follicular B lymphocytes, lymphocytes in submucosal tissues of lingual tonsil, and spermatogenic cells. Using peripheral mature B lymphocytes, the expression of TAS1R3 in B lymphocytes was further confirmed by real-time PCR and sequencing of the real-time PCR product.     

The surface structure of the completely and incompletely orthokeratinized oral epithelium in the rat: a light, scanning and transmission electron microscope study.

Mucosa from the hard and soft palates, molar gingiva, cheek and dorsal surface of the tongue of the rat was examined in the light microscope, following Mallory's triple connective tissue stain, and in the scanning and transmission electron microscopes. The epithelium covering the hard palate, gingiva, the smooth band of mucosa at the junction of the hard and soft palates, intermediate zones of the soft palate, fungiform papilla-like structures in the central zone of the soft palate, the fungiform papillae, and the more superficial part and posterior surfaces of the filiform papillae of the tongue all exhibited complete orthokeratinization. The oral surfaces of the epithelial cells in all these areas had a honeycomb pattern of interconnecting ridges surrounding depressions. Imprints of the overlying cells that had been desquamated were apparent, and the lateral boundaries between the cells were formed by two raised ridges separated by a gap. The epithelium covering the cheek, central zone of the soft palate apart from the fungiform papilla-like structures, lateral zones of the soft palate, gingival crevice, and the mucosa between the fungiform and filiform papillae of the tongue all exhibited incomplete orthokeratinization. The oral surfaces of the epithelial cells in all these areas were relatively smooth and did not exhibit a honeycomb pattern of interconnecting ridges. Imprints of the overlying cells that had been desquamated and the lateral boundaries between the cells were only very occasionally found. In the transmission electron microscope the outlines of the cells were compatible with the surface patterns seen in the scanning electron microscope. The possible relationships between the degree of orthokeratinization and ultrastructure of the various epithelia are discussed.     

Scanning-electron-microscopic study of the dorsal lingual surface of the squirrel monkey

The structure of the lingual papillae and the ultrastructure of the surface of the lingual dorsal epithelial cells of squirrel monkeys were observed by scanning electron microscopy. Filiform papillae were distributed over the entire dorsal surface of the tongue, except for the radix zone. Fungiform papillae were scattered among these filiform papillae. In the middle of the posterior end of the lingual body, a single vallate papilla was located. Higher magnification of the lingual dorsal epithelium revealed that prominent microridges and elevated intercellular borders occurred widely in the basofrontal area of the filiform papillae, interpapillar area and lingual radix zone. On the surface of the upper part of the filiform papillae, fine pits and hollows were observed. Indistinct microridges were distributed over the surface of the fungiform papillae.     

Fine structure of the dorsal lingual epithelium of the frog, Rana rugosa

Scanning and transmission electron microscopy was employed to investigate the ultrastructure of the lingual dorsal epithelial cells of the frog, Rana rugosa. The specimens for scanning electron microscopy were prepared by a method that involved osmium postfixation and treatment with acid to remove extracellular material that adhered to the surface of the tongue. Over almost the entire dorsal surface, filiform papillae, consisting of a large number of non-ciliated cells with microridges and a very small number of ciliated cells, were compactly distributed. Fungiform papillae were scattered among these filiform papillae. A round sensory disk was located on the top of each fungiform papilla. Each sensory disk was encircled by a band of ciliated cells. Transmission electron microscopy revealed that a large part of the filiform papillar epithelium was composed of cells that contained numerous electron-dense granules. These cells were coincident with the non-ciliated cells observed by scanning electron microscopy. In these cells, the nucleus was located on the basal side, and the ergastoplasm was well-developed on the basal side of the nucleus.     

SEM study on the dorsal lingual surface of the common tree shrew, Tupaia glis.

The dorsal lingual surface of the common tree shrew was examined by SEM after treating it with HCl to remove the mucous substance. Filiform (FI), fungiform (FU) and circumvallate papillae (CI) were observed. The FI exhibited a small circular bulge surrounded by anterior and posterior filamentous processes. FU were scattered among the FI. There were 3 CI separating the anterior 4/5 from the posterior 1/5 of the tongue. In addition, a group of conical projections with caudal orientation was found anterior to the palatoglossal fold on each side of the tongue. Microridges were widely observed on the entire dorsal lingual surface, except on the free surface of FI processes.     

Fine structure of the dorsal lingual epithelium of the little tern, Sterna albifrons Pallas (Aves, Lari).

The dorsal surface of the tongue of the little tern, Sterna albifrons, has a distinctive anterior region for five-sixths of its length and a terminal posterior region. The anterior region observed by scanning electron microscopy is distinguished along its forward half by a median line from which median papillae protrude. The hind half of the anterior region has a median sulcus without papillae. The deciduous epithelium on both sides of the median line and sulcus bears scattered epithelial protrusions. The posterior lingual region has neither median papillae nor deciduous epithelium. So-called giant conical papillae are located in a transverse row between anterior and posterior regions. Delicate microridges adorn the surfaces of all outer epithelial cells in both regions. Examination of the dorsal lingual epithelium by light and electron microscopy provides histologic and cytologic criteria for distinguishing anterior and posterior regions. Basal cells are nearly alike throughout the dorsal epithelium. Intermediate layer cells of the anterior region contain numerous tonofibrils in electron-dense bundles composed of 10 nm tonofilaments. The outer layer is composed of electron-dense, well-keratinized cells, and electron-lucent epithelial protrusions are present on the exposed surface of the outermost cells. Median papillae are composed of typical keratinized cells, which are nearly filled with keratin filaments. Intermediate layer cells in the posterior region of the tongue are nearly filled with unbundled tonofilaments. There is only a very thin outer keratinized layer in this region.     

Anatomical and scanning electron microscopic characteristics of the oropharyngeal cavity (tongue,palate and laryngeal entrance) in the southern lapwing (Charadriidae: Vanellus chilensis,Molina 1782)

This investigation aimed to determine the morphological characteristics of the tongue, palate and laryngeal entrance of southern lapwing by gross anatomy and scanning electron microscopy. For this purpose, the organs of three birds were used as material. Numerous densely distributed acicular projections were found on the lingual apex. Papillary crest consisting of sharp conical papillae were observed between the body and root of the tongue. Conical papillae of the lateral border of the papillary crest were triangular in form, and other conical papillae of the papillary crest were shorter in form. There were no papillary projections or papillae on the smooth surfaces of the lingual body and radix. On the median part of the palate, larger conical papillae, which were directed caudally, also surrounded entrance of the choanal cleft. The transversal papillary rows of conical papillae were observed between the rostral and caudal parts of the choanal cleft and on the caudal border of the infundibular cleft. The laryngeal entrance was surrounded by smooth mucosa without conical papillae. However, in the caudal border of the glottic fissure, there was a conical papillary row formed by numerous conical papillae. There were no anatomical differences between female and male birds.     

崇安草蜥舌的显微和超微结构

采用显微技术观察了崇安草蜥(Takydromus sylvaticus)舌的显微和超微结构.舌腹面黏膜光滑;背面黏膜粗糙,由丝状乳头和轮廓乳头组成.丝状乳头锥体形,数量较多,排列成行,分布于舌体背面两侧和侧翼的腹面.在舌的横切片上有3～7个轮廓乳头,其表面平整,周围有环形沟,舌腺开口于环形沟中.舌肌肉发达.超微结构显示,舌上皮细胞问具有紧密连接,舌乳头细胞表面具有丰富的微绒毛.舌腺为单管泡状腺,分泌管由单层柱状上皮构成.柱状上皮细胞有两种,一种为分泌细胞,一种为暗细胞.分泌细胞内有典型的分泌颗粒,可协助食物的吞咽.暗细胞内无分泌颗粒,是否与离子分泌以及渗透压调节有关,尚需进一步证实.     

EPIDERMAL FEATURES AND SILICA DEPOSITION IN LEMMAS AND AWNS OF ZIZANIA (GRAMINEAE)

In four species of Zizania (Gramineae: Oryzeae) epidermal features of pistillate and staminate lemmas, paleas, and awns were studied by scanning electron microscopy (SEM) and energy dispersive X-ray analysis. Features observed were silica bodies, siliceous papillae, pitted siliceous papillae, stomata, microhairs, and prickle hairs. Staminate lemmas have all of these features. Pistillate lemmas have silica bodies and prickle hairs, lack stomata, and differ among species in occurrences of microhairs and siliceous papillae and pitted siliceous papillae. Awns of pistillate lemmas have silica bodies, prickle hairs, microhairs, and stomata; therefore, they possess a more complete set of features than their attached lemmas. Shapes of silica bodies on pistillate lemmas differ among species. A taxonomic key based on SEM observation of pistillate lemmas separates the four species by the shapes of silica bodies, arrangement of prickle hairs, and occurrences of microhairs and siliceous papillae. The main silica-containing structures are silica bodies, siliceous papillae, pitted siliceous papillae, and to a lesser extent prickle hairs. Pitted siliceous papillae with circular raised rims are formed by collapse or exfoliation of the tops of siliceous papillae; these have not been previously described in grasses. Comparison of epidermal features in the lemmas and leaves of Zizania shows that the former lack three kinds of nonsilicified papillae and epicuticular wax that are present on the latter but the lemmas have siliceous papillae and pits that are absent in leaves.