Palatal epithelium

TJ have also been demonstrated by the lanthanum technique in the palatal epithelium (Martin, Appleton et al. 1987). These TJ could be made permeable if the yeast Candida albicans was inoculated between an acrylic plate prosthesis and the palatal epithelium this was not the case if the palate was exposed to the yeast in the absence of the prosthesis. Similarly, the presence of TJ was shown in the uppermost layer of the stratum granulosum in the lingual epithelium (Holland, Zampighi et al. 1989). 

In the squamous/stratified epithelium covering, the palatal aperture of the N-P canals and the dorso-lateral surfaces of the papilla, there are occasional clusters of taste buds. These non-olfactory chemosensory elements are positioned at or near to the entrance to the AOS, suggesting that some initial chemosensation may arise from the sampling of material... 

The cheeks, lips, hard and soft palates and tongue form the oral cavity. The main difference between the oral mucosa and skin as compared to the gastrointestinal (GI) tract lining lies in the organization of the different epithelia. While the latter has a single layer of cells forming the simple epithelium, the skin and the oral cavity have several layers of cells with various degrees of differentiation. 

The thickness of the buccal epithelium varies from 10 to about 50 cell layers in different regions because of serrations in connective tissue. In fact, the thickness of buccal mucosa has been observed to be 580 pm, the hard palate 310 pm, the epidermis 120 pm, and the floor of mouth mucosa 190 pm. 

Keratinized epithelium is dehydrated, mechanically tough and chemically resistant. It is found in areas of the oral cavity subject to mechanical stress such as the mucosa of the gingiva (gums) and hard palate (roof of mouth). Non-keratinized epithelium is relatively flexible and is found in areas such as the soft palate, the floor of the mouth, the lips and the cheeks. Thus the regions of the oral cavity pertinent to drag delivery (i.e. the sublingual and buccal regions) have a non-keratinized epithelium. 

The mechanism of olfaction has many theories but is not fully understood and is still the subject of research. The nose is the human organ that detects smell (Fig. 5.9). It extends from the face to the end of the palate. In its simplest explanation the two nasal cavities are lined with a mucous membrane, kept moist by the secreted substance mucus. Chemicals in the air entering the nose must dissolve in this mucus before they can be detected. A small area - about the size of a small postage stamp - in the upper part of the nasal cavity contains olfactory cells, which are sensitive to the chemicals in the mucus solution. For a molecule to be detected it must bind specifically to the sensitive cells that act as sensory receptors. The sensory receptors situated in the olfactory epithelium (epithelium is the name given to the outer layer of covering cells) are believed to bind specifically with substances according to the shape of their molecules. 

The two subunits of the sweet taste receptor are differentially distributed in the gustatory epithelium. T1R2 is expressed most frequently in taste buds of the cir-cumvallate and foliate papillae (Hoon et al. 1999), less so in palatal taste buds... 

Sun, D., Vanderburg, C.R., Odierna, G.S., Hay, E.D. 1998. TGFbeta3 promotes transformation of chicken palate medial edge epithelium to mesenchyme in vitro. Development 125, 95-105. 

Snakes were anaesthetized with urethane (2 g/kg) injected i.p. and secured in a Kopf sterotaxic instrument equipped with a specially designed snake restraint. The vomeronasal epithelium was exposed by removing the medial palate and mushroom body. The nasal cavity was exposed by removing part of the mucosa of the roof of the mouth. For recording single units in the MOB and AOB, the cranium was opened dorsally and the bulb exposed (Figure 1). 

The vomeronasal organ contains sensory afferents of a system that appears to be especially important in the detection of socially relevant chemical signals. The organ is physically separate from the olfactory epithelium and resides at the base of the nasal septum or in the hard palate. 

For the study of VNO-mediated chemosensory phenomena the elephant offers distinct advantages because of its trunk, which makes the flehmen response clearly defined and easy to identify and count. Both sexes of Asian elephants have a cigar-shaped paired vomeronasal organ located dorsal to the hard palate. Paired orifices lead into the anterior mucous-filled respiratory epithelium region, which connects in turn with the neuroepithelial area (Rasmussen, unpublished). 

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