Okajimas Folia Anat. Jpn., 63 (4) 179-192, October 1986 Scanning Electron Microscopic Study on the Plicae Palatinae Transversae and their Microvascular Patterns in the Cat By Isumi TODA Department of Anatomy, Osaka Dental University 1-47 Kyobashi, Higashi-ku, Osaka 540, Japan (Director: Prof. Y. Ohta) (with 1 text-figure and 14 figures in 3 plates) -Received for Publication, June 25, 1986- Key Words: Transverse palatine ridge, Hard palate, SEM, Plastic injection, Cat Summary: The microvasculature in the plicae palatinae transversae of the hard palate of the cat was investigated by means of the acryl plastic injection method under a scanning electron microscope (SEM). On the hard palate of the cat, seven or eight transverse palatine ridges arching forwards were observed. Small digitiform processes were located on the top line of each ridge, and anterior and posterior conical processes were present on both the anterior and posterior slopes of each ridge. The lateral ends of each ridge were observed as simple forms in which these processes disappeared. The blood supply of the ridges came from the lateral and medial branches of the a. pala- tina dura major. These branches formed a primary arterial network in the submucosa super- ficial to the palatine venous plexus. Small twigs were derived from this network to form a secondary arterial network in the lamina propria. Further, arterioles from this network formed a subepithelial capillary network immediately beneath the epithelium. From this net work, capillary loops sprouted into the papillae of the lamina propria. Blood from the subepithelial capillary network drained into the primary venous network in the lamina propria, from which venules drained into the superficial layer of the palatine venous plexus in the submucosa, and then into its deeper layer. The entire microvascular pattern of the hard palate of the cat was thus investigated and used to assess and confirm the lamina-formation of the palatine mucosa. Regions of thickening such as the transverse palatine ridges of the cat were not formed by thickening of the lamina propria, but by the submucous tissue including the vascular complex. General pictures of the fine vasculature mucosae, the hard palate is covered with an of the mucosae of many organs have been immovable mucosa, in which the border obtained by various methods. In particular, between the lamina propria and the sub- Tsudomi (1963) investigated that of the mucosa is not obvious, and submucosal digestive mucosae in relation to their histo- tissue is not present. logical structure. However, the structures On the hard palate of the cat, the plicae of the oral mucosa differ from those of palatinae transversae, which are peculiar to other digestive mucosae, such as of the eso- this species, are located in a regular fashion. phagus, stomach, etc. Among the oral The blood supply to the palate of the cat 179 1 80 I. Toda has been described by Hiirlimann (1913), scanning electron microscope (JSM-T300, Davis et al. (1943), Miyazaki (1960) and JEOL, Tokyo). Sawa (1961), although they did not eluci- 2) Histologicalslides of the injected materials date its microvasculature at the SEM level. Using two other cats, acryl plastic was The present paper deals three-dimension- injected by the above procedures. The in- ally withthe microvasculature of the pala- jected palatine tissues were then fixed in tine ridges in microcasts, in relation to the . 10% formalin, embedded in celloidin and surrounding layers of the mucosa in histo- cut for serial sections of 10 pm thick. Every logical slides of injected materials. By fifth slide was stained with hematoxylin. elucidating the laminar structures of the These slides were employed to observe re- microvascular patterns of the hard palate , lations between the vascularpatterns and the it should be possible to confirm the lamina- surroundingstructures. formation of the histological structures . 3) SEM specimens of the palatine mucous surface Materials and Methods Two cats were perfused from the carotid arteries with 2.5% glutaraldehyde. The Twenty adult cats were employed for this material from one cat was post-fixed with study.They were bled to deathafterinject- 2% osmic acid, treated in the critical point ing heparin intravenously. The following dryer and coated with gold for SEM, and specimens were employed. was mainly employed for comparison with 1) Casts of the vascular patterns of the the plaster model. The other material was palatine region prepared for serial sections of 15 Am thick Acryl plastic was injected into the caro- after celloidin-embedding,and stained with tid arteries of ten cats by means of the hem atoxylin -e osin . plastic injection method (Taniguchi, Ohta et al., 1952, 1955). Plaster models were Findings made by taking an alginate impression of the palatine mucous surface. The injected I. Macroscopic features of the plicae pala- palatine tissues were then treated with tinae transversae sodium hypochlorite solution to remove the On the hard palate of the cat, seven soft tissues and so obtain microcasts of their or eight plicae (ridges) palatinae transversae vascular patterns. arched anteriorly (Figs. 2, 3), and each end Using another six cats, red colored plastic of them curved posterolaterally. They were was injected into the ascending aorta and mostly observed as symmetrical arches, blue colored plastic into the vena cava although they rarely branched at their ends superior. The injected palatine region was or adhered with each other (Fig. 4). treated with 10% sodium hydroxide in order The anterior slope of each ridge was longer to obtain casts of its vascular pattern. The than the posterior slope, so that the post- two-colored casts were used for exami- erior slope was somewhat steeper. In the nation of the differences between the arterial median one third of each ridge, small digiti- and venous elements. form processes (about 500 gm in height, All these casts were observed primarily and about 300 Am in basal diameter) were under a stereoscopic dissection microscope observed along its top line. These processes to cut down the microcasts in the palatine were more distinct near the median line, region. The materials dissected out were but became smallernear the end of the ridge coated with gold for examination under a (Figs. 2, 3). On the anterior and posterior SEM Study on the Plicae Palatinae Transversae in the Cat 181 slopes, anterior and posterior conical pro- in the posterolateral region was defective cesses (about 700 pm in height, and about and the superficial layer was in direct con- 500 ,um in basal diameter) (indicated as tact with the periosteum (Fig. 6). small triangular processes by Iwaku (1976)), The whole venous plexus was composed numbering 14 — 20, were located regularly of venous vesselsrunning sagittally. Venous parallel to the ridge. These two kinds of vesselscommunicating between the plexuses processes became smaller laterally and dis- of both sides were observed in the super- appeared at the lateral end of the ridge ficial layer, much more especially in the (Figs. 2, 3). ridges. No palatine gland was observed in the hard palate of the cat. II. Histological features of the plicae pala- tinae transversae III. Vascular patterns of the plicae pala- The stratified squamous epithelium cover- tinae transversae ing the hard palate was similar in thickness 1. Arterial system all other with thin keratinizations. The 1) General aspect in the hard palate (Fig. 1) lamina propria was also similar in thickness The a. palatina dura major (Sawa, 1961) except for a slightly thicker area on the ran on the bone surface in the posterior ridges. Both small digitiform and conical third of the hard palate and superficial to processeswere formed by protrusions of the the palatine venous plexus in the anterior lamina propria itself. The papillae on the two thirds, and en route gave rise to the ridge and hese processes were highest on medial and lateral branches (Sawa) (Fig. 7). the anterior side and lowest on the posterior Each of these branches ran medially or side with a smaller number (Fig. 5), and laterally in a layer superficial to the sub- those between the ridges were usually low. mucous tissue and the venous plexus, imme- They becamelower at the lateral end of each diately beneath the palatine ridge. They ridge with disappearance of the processes formed the submucous arterial network, that is, the primary arterial network. This (Fig. 6). The submucous layer was similarin thick- was formed directly in contact with the ness to the lamina propria. It can be said to periosteum in the posterolateral region of the hard palate due to the lack of the divide into superficial and deep layers. The superficial layer was composed of con- venous plexus. Part of the primary network siderably dense connective tissues including in the anterior one third of the hard palate the palatine venous plexus formed by finer was developed into the incisive arterial venous vessels. This layer became thicker in network (Sawa) (Fig. 7) since the medial and lateral branches were usually so thick proportion to the height of the ridge except in both processes (Fig. 5). Almost all of the that they were often similar to the a. pala- deep layer was occupied with the palatine tina dura major. venous plexus formed by thick venous vessels From the primary, submucous arterial and directly lined by the periosteum (Fig. 5). network, small twigs were derived towards This layer was mostly similar in thickness the epithelial surface. They ramified tan- all over the hard palate. The venous plexus gential to the surface between the sub- in this layer was observed only beneath the mucosa and lamina propria, and formed an ridges in the anterior half of the hard palate, incomplete, arterial network in the lamina and only in the median regionof its posterior propria, that is, the secondary arterial half, not in the posterolateral regionsof both network (Fig.