Scanning Electron-Microscopic View of the Oral and Basal Epithelial Surfaces of the Rat Soft Palate

Abstract

We studied corresponding structures on the oral and basal surfaces of the oral epithelial layer, focusing on the microanatomy of gustatory papillae. Specimens for scanning electron microscopy were obtained from the rat soft palates and fixed with a mixture of 2% paraformaldehyde and 1% glutaraldehyde. They were first prepared without postfixation and conductive-staining to study the oral surface. After examination, the epithelium was reinforced by additional sputter coating and treated with 6 N NaOH at 60°C to exfoliate the basal epithelial surfaces without any significant artifacts. The papillae, showing circular, elliptical or fusiform protuberances on the oral surface, were classified into two types: types I and II. The type I and type II papillae contained one and two taste pores, respectively. On the basal epithelial surface, the basal portions of the taste buds were associated with concentrically arranged nerve fibers and Schwann cells. Another characteristic finding on the basal epithelial surface was the presence of excretory ducts of minor salivary glands in a close spatial relationship to taste buds. It is suggested that saliva coming out through the duct is mixed with food, thus enabling intimate contact with the taste pores of the papillae.

Structural and Ultrastructural Characteristics of the Red-Rumped Agouti (Dasyprocta leporina—Linnaeus, 1758) Palatine Epithelium

“…The lamina propria shows interdigitating in the hard palate as in dog, pig, rat, rabbit, guinea pig, sheep, buffalo (Sa et al, 2016), Egyptian goat (Mahdy et al, 2018), rocky cavy (Aro et al, 2019), and Anatolian bobcat (Ari & Uslu, 2019). In the soft palate, the presence of gland clusters is similar to the findings for Wistar rats (Sakai et al, 2001).…”

“…The epithelial surface amplified by scanning electron microscopy enables to characterize the hard palate ridges as smooth and different from Wistar rat conical papillae intermolar composition (McMillan, 1979), whilst the soft palate of Wistar rat also differs by the presence of gustatory papillae and three distinct morphological regions (Sakai et al, 2001). The epithelial desquamation was also seen in Egyptian goats, which is associated with the mechanical loads on the epithelium during the deglutition (Mahdy et al, 2018).…”

“…In the transition zone between the hard and soft palate, palatine ridges become smaller and it is similar to those seen in African squirrels (Eisentraut, 1975). The soft palate has no palatine ridges, is smooth and uniform, as in the rocky cavy (De Aro et al, 2019), and distinct from the Wistar rat (Sakai et al, 2001).…”

“…The palatal mucosa structural composition consists of a keratinized stratified epithelium, composed of layers and lamina propria below the epithelium. The hard palate has bone support (Mahdy et al, 2018;Ari & Uslu, 2019), while the soft palate has gland clusters in the submucosa (Sakai et al, 2001). Both regions are characterized by the presence of nerve fibers and mechanoreceptors .…”

Structural and ultrastructural characterization of the palatine epithelium of the Guinea pig: A new record of telocytes in the oral cavity

“…The soft palate has no palatine ridges and is divided into distinct morphological regions in Wistar rats, it presents clusters of salivary glands and lacks bone support, providing greater mobility and assisting in swallowing (Sakai, Morino, & Inoué, 2001).…”