Scanning Microscopy Volume 7 Number 4 Article 21 10-21-1993 Scanning Electron Microscopic Studies of the Palatine Mucosa and Its Microvascular Architecture in the Rat S. Sugioka Osaka Dental University H. Ike Osaka Dental University Follow this and additional works at: https://digitalcommons.usu.edu/microscopy Part of the Biology Commons Recommended Citation Sugioka, S. and Ike, H. (1993) "Scanning Electron Microscopic Studies of the Palatine Mucosa and Its Microvascular Architecture in the Rat," Scanning Microscopy: Vol. 7 : No. 4 , Article 21. Available at: https://digitalcommons.usu.edu/microscopy/vol7/iss4/21 This Article is brought to you for free and open access by the Western Dairy Center at DigitalCommons@USU. It has been accepted for inclusion in Scanning Microscopy by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. Scanning Microscopy, Vol. 7, No. 4, 1993 (Pages 1321-1332) 089 l-7035/93$5.00+ .00 Scanning Microscopy International, Chicago (AMF O'Hare), IL 60666 USA SCANNING ELECTRON MICROSCOPIC STUDIES OF THE PALATINE MUCOSA AND ITS MICROV ASCULAR ARCHITECTURE IN THE RAT S. Sugioka and H. Ike• Department of Anatomy, Osaka Dental University, 1-5-31 Otemae, Chuo-ku, Osaka 540, Japan (Received for publication July 25, 1993, and in revised form October 21, 1993) Abstract Introduction Detailed observations were made on the structure The palatine mucosa, designated the masticatory and microvasculature of the palatine mucosa of the rat mucosa, may have special morphological and functional by means of microvascular corrosion casts and epitheli­ elements that contribute to the mastication and swallow­ um-digested specimens using scanning electron micros­ ing of food. These elements may function in close co­ copy. The rat palate was divided into four regions ac­ operation with the mucous membrane of the lingual dor­ cording to the characteristics of the palatine plicae. In sum. Recently, the morphology and function of the pal­ the atrial region, no transverse palatine plicae were pre­ atine mucosa and its microvasculature were comparative­ sent, but there were longitudinal ridges and folds in the ly studied in mammals (Toda, 1986; Kajiwara, 1989; median area. These structures contribute to the trans­ Ike, 1990; Inoue and Toda, 1991; Aharinejad and portation of rough and grainy foods with the assistance Lametschwandtner, 1992) giving consideration to the of the hairy buccal part. Capillary loops in the ridge food habits of the species studied. Ohta et al. (1992) and folds appeared as continuous, sagittally elongated published a review on the oral mucosa and its microvas­ loops. In the palatine fissure or antemolar region, only culature in mammals, referring especially to scanning three typical transverse palatine plicae contribute to the electron microscopy (SEM) of the palatine mucosa. Ro­ regurgitation of food. Capillary loops appeared in vari­ dents generally have a sagittally long and narrow palate. ant forms on the top, and the anterior and posterior Since the area between the upper incisors and incisive slopes of the plicae. Venous palatine plexus was ob­ papilla in the rat grows postnatally, it is extremely nar­ served only in the palatine fissure region. In the inter­ rowed and covered by the hairy buccal swellings almost molar region, each of the five transverse plicae was up to the median line. From the upper incisors to the composed of many wedges arranged sagittally. These soft palate, there are four kinds of the transverse pala­ plicae contribute to the transportation of food toward the tine plicae and protrusions. It can be said that such larynx. Capillary loops in the plica were in the shape of morphological characteristics of the palatine mucosa may complicated villi. Filiform protrusions or papillae were be recognized in company with the local distribution of aggregated immediately posterior to the last plica. The various lingual papillae. These must contribute to the capillary loops appeared as typical hairpins. They con­ combined function of the prehesile organ, and masticato­ tribute to swallowing of food with active assistance from ry or mashing apparatus preceding the swallowing of the epithelial eminence of the lingual dorsum. Palatine food (Kuramae, 1989; Ohta et al., 1992). We attempted plicae showed considerable local differences, which may to investigate specially differentiated structures of the contribute to the prehension, transportation, and mashing palatine mucosa and their microvasculature in the rat by of food. combining SEM studies of microvascular corrosion casts and epithelium-digested specimens. Key Words: Microvasculature, palatine mucosa, trans­ verse palatine plica, scanning electron microscope, Materials and Methods vascular corrosion castings, rat. • Address for correspondence: Twenty adult Wistar rats were used. They were Hiromi Ike anesthetized with sodium pentobarbital (Nembutal®; 40 Department of Anatomy, mg/kg body weight). The ascending aorta was cannu­ Osaka Dental University lated via the left ventricle and the blood vascular system 1-5-31 Otemae, Chuo-ku, of the head and neck was washed with 30 ml heparinized Osaka 540, Japan (5,000 IU/1) saline solution at 40°C until the efflux of Telephone No. 81-6-943-6521 the superior vena cava became clear. The following FAX No. 81-6-943-8051 specimens were prepared: 1321 S. Sugioka and H. Ike Epithelial surface and epithelium-digested Figure 1. The whole aspect of the palate. Four regions specimens: The palatine mucosa of five rats was imme­ (a-d) are marked off by lines. (a) Incisor-incisive rsion-fixed with 2 % glutaraldehyde and postfixed with papillary/ atrial region: It is narrow and covered by l % osmium tetroxide, then freeze-dried in t-butyl alco­ hairy buccal parts (8). No transverse palatine plicae are hol after dehydration in a graded series of ethyl alcohols observed but the atrial ridge (arrowhead) and folds (ar­ (Inoue and Osatake, 1988), and coated with gold for rows) pass sagittally along the median line. (b) Palatine SEM examination. In some of the aldehyde-fixed speci­ fissure/ antemolar region: Three typical transverse pala­ mens the epithelial layer was separated from the lamina tine plicae are observed. Location of the palatine fis­ propria by treatment with 5 N KOH at room temperature sures are shown by dotted lines. (c) Intermolar region: for 3- 7 days. This material was subsequently prepared Five transverse palatine plicae are observed. The for SEM observation after postfixation and freeze-drying wedges that make up each plica are not recognized be­ as described above. cause it is covered by a stratified squamous epithelium Microvascular corrosion casts: Thirteen rats (compare with Figure 2 on an epithelium-separated spec­ were used for the cast preparation. Methyl methacrylate imen). ( d) Boundary region between the hard and soft plastic (viscosity: 23 centipoises, 70% glycerin at 20°C) palates. High and numerous filiform protrusions (A) in the condition of oligomer by heating at 85°C was in­ aggregate together. Bar = 2 mm. jected with a plasticizer (20% dibutyl phthalate) via a Figure 2. The whole lamina propria of the palate on an cannula inserted into the ascending aorta according to epithelium-separated specimen. Wedges, composing the plastic injection method of Ohta et al. (1990). The each transverse plica are compressed in a right-left di­ injected material was left for 3-4 hours at room tempera­ rection and separated from each other in the intermolar ture. After the plastic had polymerized, the palate, in­ region but continuous in the palatine fissure region. cluding the inferior nasal cavity, was dissected out. Filiform protrusions (arrow). Bar = 2 mm. This material was treated with 10% NaOH to digest soft tissue and obtain microvascular corrosion casts. The Figure 3. Microvascular cast of the incisor-incisive specimens were coated with gold and examined in a papillary and palatine fissure regions. The inset shows JEOL JSM-T300 SEM operated at accelerating voltages ends of the major palatine arteries (arrows), palatine of 5 or 25 kV. venous plexus (V), veins (arrowheads), and the lateral (L) and medial (M) branches. Incisive papilla (P). Bars Histological slides: The palates of two rats were = 2 mm. dissected out after perfusion of 10% formalin solution via the left ventricle. This material was embedded in celloidin after dehydration in a graded series of ethanol was located at the anterior end of the palatine fissure and serially sectioned (30 µm thick) in the sagittal and (fissura palatina: NAY, 1975, or anterior palatine fora­ frontal directions, and stained with hematoxylin-eosin. men: Greene, 1968), and a pair of the nasopalatine canals opened close to the papilla. Results The surface of the stratified squamous epithelium was keratinized, showing no regional differences in Macro- and microscopic structures of the palatine thickness. The boundary zone between the well-devel­ mucosa oped lamina propria and submucous tissue was not undu­ lated. Connective tissue papillae of the lamina propria The whole rat palate appeared as an elongated generally were not developed except in the incisor-inci­ isosceles triangle with a square added posteriorly. The sive papillary (atrial) region, the plical ridges of the apex of the triangle was located at the incisive papilla, palatine fissure region, and boundary between the hard and its base was at the mesial level between the anterior and soft palates. molars (Figs. I and 2). The area between the incisors Typical, transverse palatine plicae or ridges were and the incisive papilla (Fig. 3), a characteristic feature located in the anterior half of the hard palate, and fili­ of the rat, was called the atrial region by Kutuzov and form papillae in the posterior half as a characteristic of Sicher (1952). Anterior to the papilla, a long mucous this specimens (Fig. I). The properties of the hard pala­ median ridge passed up to the posterior surface of the in­ tine mucosa were described by dividing it into 4 regions cisors, straight along the median line, and usually was (Fig.