Vascular network in papillae of dog oral mucosa using corrosive resin casts with scanning electron microscopy.код для вставкиСкачать
THE ANATOMICAL RECORD 226:447-459 ( 1990) Vascular Network in Papillae of Dog Oral Mucosa Using Corrosive Resin Casts With Scanning Electron Microscopy YOSHIAKI KISHI, KAZUTO TAKAHASHI, AND HENRY TROWBRIDGE Department of Oral Anatomy, Kanagawa Dental College, Inaoka, Yokosuka, Japan (Y.K., K.T.);Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia (H.T.) ABSTRACT The purpose of this study was t o undertake a three-dimensional analysis of the vascular network of the lamina propria in the gingiva, alveolar mucosa, buccal mucosa, palate, and lingual mucosa of the dog. Using the corrosive resin casting technique, casts of the vascular network were prepared and examined by scanning electron microscopy. In the oral mucosa, larger arteries in the submucosa divide into smaller branches that enter the lamina propria. These branches form one or more layers of vessels a t the base of the papillae of the lamina propria, the so-called subpapillary vascular network. Here the vessels divide again and enter the papillae to form a subepithelial capillary network. The configuration of the capillary loops within each papilla of the lamina propria is determined by the shape of the papilla. The characteristic shape of the loops resembles a hairpin. The capillary loops in the lingual papillae are larger and more complex than capillary loops found elsewhere in the oral mucosa. The mucosa of the posterior portion of the hard palate, the soft palate, and the tongue contain many venous valves. The basic structure of mucous membrane varies in enter the lamina propria and divide to form a subepidifferent areas of the oral cavity in accordance with thelial capillary network in the papillae. Veins arising functional demands. There are three basic types of oral from the capillary loops follow the course of the arteries. The tongue consists of a core of connective tissue and mucous membrane: masticatory mucosa, lining mucosa, and specialized mucosa. Masticatory mucosa sur- skeletal muscle, which is covered by the lingual murounds the teeth and covers the hard palate and is thus cosa. The mucosa consists of a submucosa that overlies subjected to the major forces of mastication. Hence the the muscle and a lamina propria that is covered by surface epithelium is keratinized and the lamina pro- epithelium. The anterior portion of the dorsal lingual pria is thick, dense, and firm. The submucosa of the mucosa contains numerous lingual papillae and taste gingiva contains coarse collagenous bundles that ex- buds. These lingual papillae are formed by the projectend from the bone to the lamina propria. The submu- tion of small, nipple-shaped elevations of the conneccosa of the hard palate is well defined and tightly tive tissue (i.e., papillae of the lamina propria) into the bound to the periosteum of the palatal and maxillary overlying epithelium, thus producing evaginations of the mucous membrane. Five types of lingual papillae bones. Lining mucosa of the oral cavity is associated with can be distinguished on the dog tongue: filiform, fungithe lips, cheeks, vestibule, floor of the mouth, under- form, foliate, circumvallate, and conical (lenticular). surface of the tongue, alveolar process, and soft palate. Each type has its own characteristic microvasculature. It is generally recognized that the blood supply to the The surface epithelium of this type of mucosa is relatively thick and unkeratinized, and the lamina propria tongue is more plentiful than to most other tissues of is thinner and less dense than that of the masticatory the body (Hellekant, 1971). The upper surface of the mucosa. Specialized mucosa is found on the dorsum of tongue receives its blood supply from the vertical branches of the profound lingual artery, which is a conthe tongue and contains taste buds. The lamina propria of mucous membrane contains tinuation of the lingual artery. Together with branches papillae that indent the overlying epithelium. These from the dorsal artery, the vertical branches of the propapillae contain capillaries as well as nerve fibers. They vary in length and width in different regions of the oral mucosa. While in the gingiva the papillae are characteristically tall and slender, papillae of the alveReceived September 6, 1988; accepted July 18, 1989. olar mucosa, hard and soft palates, and buccal mucosa Address reprint requests to Henry Trowbridge, Ph.D., Department are low in height. of Pathology, School of Dental Medicine, University of Pennsylvania, Tributaries of the larger arteries in the submucosa Philadelphia, PA 19104-6002. 0 1990 WILEY-LISS, INC. 448 Y. KISHI ET AL. Figs. 1-4. VASCULAR NETWORK OF ORAL MUCOSA 449 Fig. 5. Sagittal section of the vascular network of buccal mucosa. a, arteriole; v, venule; spcn, subpapillary capillary network; M, muscle. Bar = 100 pm. Fig. 7. External view of the vascular architecture of buccal mucosa. Note relatively high density of capillary loops. Star indicates orifice of minor salivary gland duct. Bar = 100 pm. Fig, 6. Resin cast shown in Figure 5 as seen from the opposite side. a, arteriole; v, venule; spcn, subpapillary capillary network. Bar = 100 pm. Fig. 8. Capillaries of buccal mucosa showing simple loops. a, ascending limb of capillary loop; v, descending limb of loop. Bar = 100 pm. Fig. 1. Vascular network, gingiva, showing distribution of venules (V) and arterioles (A) in lamina propria. Cr, location of tooth crown. Bar = 1,000 pm. Fig. 2. Vascular network in the lamina propria of the marginal (free) gingiva. The capillary bed consists of characteristic capillary loops that resemble a hairpin. a, ascending limbs of capillary loops; v, descending limbs of loops; Cr, tooth crown. Bar = 100 pm. Fig. 3. External view of the vascular architecture of the gingiva (G) and alveolar mucosa (AM). MGJ, mucogingival junction. Bar = 1,000 pm. Fig. 4. Relatively short capillary loops in papillae of alveolar mucosa. a, ascending limb of capillary loop; v, descending limb of loop. Bar = 100 pm. found lingual artery form two vascular plexuses, a submucosal plexus and a subpapillary plexus. The capillary network of the lingual papillae is derived from branches of the subpapillary plexus. The vascular network of the submucosa and lamina propria of the oral mucosa has received considerable attention in the literature. The vascular anatomy of the gingiva has been examined by Forsslund (19591, Egelberg (19661, Hock and Nuki (1971), Kindlova (1965), Kishi and Takahashi (19781, and Kishi (1982), whereas Klotz (1887), Schafer (19291, and Swindle and Maher (1963) studied the blood vessels of the palate. Earlier studies utilizing the microarteriographic technique developed by Takahashi (1962a,b) provided a Y. KISHI ET AL. 450 Fig. 9. Capillary loops encircling the orifice (star) of buccal salivary gland duct. Bar = 100 pm. Fig. 10. Vascular network of parotid papilla. Numerous capillary loops form concentric rings around the orifice (star) of the parotid gland duct. Bar = 100pm. general description of the microvasculature of the lingual papillae. In this paper we present the results of a three-dimensional analysis of the vascular network in the papillae of dog oral mucous membrane. Vascular casts of the microvasculature of the gingiva, alveolar mucosa, buccal mucosa, hard and soft palate, and tongue were prepared and examined by scanning electron microscopy Immediately following fixation, the tongue was resected and cannulas were inserted into the right and left lingual arteries. Mercox was injected into the cannulas under pressure to perfuse the vascular bed. After the resin had polymerized, the tissue was digested with 10%potassium hydroxide, leaving only the resin cast of the vascular network. All of the specimens were washed thoroughly with 40°C tap water and freeze-dried. After being coated with platinum-palladium, the specimens were examined under SEM. (SEM). MATERIALS AND METHODS Two adult mongrel dogs were anesthetized with sodium pentobarbital(25 mg/kg). The left and right common carotid arteries were cannulated, and Ringer’s saline solution was then perfused into the arteries until the jugular veins were cleared of blood. Glutaraldehyde (2%) in phosphate buffer (pH 7.4) was immediately injected into the carotid arteries to provide fixation of the vessels and their tributaries. Following fixation, cannulas were tied to the left and right external carotid arteries. A freshly prepared solution of a low viscosity resin (Mercox) was then injected under pressure from a specially designed syringe into the cannulas. After the resin had hardened, the jaws were removed and decalcified in 10% nitric acid for several days. The demineralized tissues were then macerated in a 10% solution of potassium hydroxide until only the resin casts of blood vessels remained. In some cases the teeth and mandible were not demineralized so that the spatial relationship between the vascular casts and the mineralized tissues could be assessed. These specimens were frozen as soon as the resin had hardened and cut into small blocks. The soft tissues were digested away by incubating the blocks a t 40°C for approximately 2 weeks in a phosphate-buffered solution (pH 8.4) containing proteinase a t a concentration of 20%.The buffer solution was changed every other day to prevent it from becoming acidic. RESULTS In the oral mucosa larger vessels in the submucosa divide into smaller branches that enter the lamina propria. The branches form one or more layers of vessels at the base of the papillae of the lamina propria, thus forming the subpapillary vascular plexus. The number of layers of vessels in this plexus varies from one area of the mucosa to another. The vascular network of the Fig. 11. Occlusal view of venous plexus (V) of the lamina propria of hard palate. Arterioles (A) can been seen running through transverse palatine ridges. Bar = 1,000 pm. Fig. 12. Venous valve in the venous plexus of hard palate. Asterisks indicate valve sinusoids. The arrow shows direction of blood flow. Bar = 100 pm. Fig. 13. External view of capillary network in papillae of mucosa of hard palate. Note well-developed transverse palatine ridges. Cr, location of tooth crown; G, capillary loops of gingiva. Bar = 1,000 pm. Fig. 14. High magnification of inset in Figure 13 demonstrating simple capillary loops. a, arterioles; v, venules. Bar = 10 pm. Fig. 15. High magnification of inset in Figure 13 showing anastomosing capillary loops in the crest of a transverse palatine ridge. a, ascending portion of capillary loop; v, descending portion of capillary loop. Bar = 10 pm. VASCULAR NETWORK OF ORAL MUCOSA Figs. 11-1 5. 451 452 Y. KISHI ET AL. Figs. 16 and 17. 453 VASCULAR NETWORK OF ORAL MUCOSA Fig. 18. Cast of capillary network in the superficial layer of the lamina propria of the dorsum of the tongue. Note numerous corolla-shaped capillary loops distributed in the filiform papillae (FP). The subpapillary network (spcn) interconnects the vessels of the papillae. Bar = 100 pm. papillae of the lamina propria consists primarily of capillary loops whose characteristic shape resembles a hairpin or horseshoe. Gingiva Examination of the vascular casts revealed that the blood supply of the gingiva is derived chiefly from branches of arteries that run along the outer surface of the alveolar bone. These vessels anastomose with branches of arteries from the periodontal ligament as well as with arteries t h a t emerge from the crest of the alveolar bone. The arteries that ascended along the surface of the alveolar bone cross the alveolar ridge, enter the gingiva, and then follow a course 700-800 pm below the outer surface of the gingiva. These arteries give off numerous branches that extend through the submucosa to form the vascular network of the lamina propria (Fig. 1). Measurements of vascular dimensions in the lamina propria beneath the papillae revealed that the diameter of casts of the arterioles ranged from 15 to 20 pm, Fig. 16. Occlusal view of the capillary network beneath soft palate mucosa. Interconnecting capillary loops encircle the orifice of excretory duct of palatine gland (asterisks). Bar = 100 pm. Fig. 17. High magnification of inset in Figure 16. Anastomosing capillary loops encircling the orifice of palatine gland duct (asterisk). a, arterioles; v, venules. Bar = 100 pm. whereas casts of the venules were considerably larger, having diameters ranging from 44 to 55 pm. Branches arising from this network form yet another layer of vessels a t the base of the papillae, the so-called subpapillary vascular network. The diameter of the casts of arterioles and venules that comprise this network was approximately 12 and 20 pm, respectively. Capillary loops in the gingival papillae consist of a n ascending arterial limb and a descending venular limb. The diameter of the descending portion of the loops is generally greater than that of the ascending portion (Fig. 2). Gingiva is divided into free gingiva and attached gingiva. The free gingival groove represents the transition zone between the free and attached gingiva. Characteristically the capillary loops in the papillae of free gingiva are the tallest of any of the capillary loops observed in various areas of the oral mucosa. In passing from the free gingiva through the transition zone to the attached gingiva, the capillary loops in the papillae become shorter and there is less space between the arterial and venular ends of the loops. No differences were noted in the subpapillary network in the free and attached gingiva. Alveolar Mucosa The gingiva is separated from the alveolar mucosa by a scalloped line, the mucogingival junction. While the gingiva is tightly bound to the underlying periosteum, the alveolar mucosa covers the outer surface of Y. KISHI ET AL. 454 Fig. 19. High magnification of filiform papilla. Capillary loops in primary papilla (I),secondary papilla (II), and tertiary papilla (111). a, ascending limb of capillary loop; v, venule; SPCN, subpapillary capillary network. Bar = 100 pm. Fig. 20. Vascular network in fungiform papilla. a, ascending limb of capillary loop; d, descending limb. Bar = 100 wm. the alveolar process and is loosely attached to the periosteum. The vascular network of the lamina propria of the alveolar mucosa was similar to that in the gingiva. However, the capillary network beneath the mucosa has a greater density and a different morphological arrangement than in the gingiva (Fig. 3). Capillary loops in the papillae of the alveolar mucosa are quite short compared with the papillae of the gingiva. They are arranged in a continuous wave-like pattern with juxtaposed rows of capillary loops running parallel to the mucogingival junction (Fig. 4). Buccal Mucosa The lamina propria of the mucosa on the cheek (buccal mucosa) consists of dense connective tissue that extends short papillae into the overlying epithelium. In general, the vascular network is less extensive than in gingiva. Examination of casts of vessels in the lamina propria revealed a network in which arterioles and venules run closely together (Figs. 5, 6). O'ften two venules run together with a single arteriole. This ar- rangement does not occur in the lamina propria of other oral mucous membranes. The diameter of the casts of the arterioles measured approximately 20 Fm, whereas many of the venules were nearly 40 pm in diameter. Thus these arterioles and venules are comparable in size t o those in the lamina propria of the gingiva. The capillaries in the papillae form typical hairpin loops that are simple and short in height. There is little difference in the diameters of the ascending and descending limbs of the loops (Figs. 7 , 8). Fig. 21. Capillary loops in fungiform papilla. a, ascending limb of capillary loop; d, descending loop. Bar = 100 pm. Fig. 22. Vascular network in folliate papilla (FP). By dissecting away the overlying superficial capillary network, a large venule (V) can be visualized. Bar = 1,000 pm. Fig. 23. High magnification of a portion of the vascular network in a folliate papilla. V, large venule; a, arteriole; v, small venule. Bar = 100 Km. Fig. 24. Vascular network of conical papilla. Asterisks indicate unique corolla-like capillary loops; d, descending venule. Bar = 100 pm. VASCULAR NETWORK OF ORAL MUCOSA Figs. 21-24. 455 456 Y. KISHI ET AL. Fig.25. 457 VASCULAR NETWORK O F ORAL MUCOSA Numerous minor salivary glands are located beneath the buccal mucosa. In general, capillary loops associated with the ducts of these glands are organized in a corolla-like pattern that surrounds the orifices of the ducts (Fig. 9). Figure 10 depicts capillary loops in the parotid papilla that surrounds the orifice of the excretory duct of the parotid gland. Numerous tall capillary loops are observed, forming several concentric rings around the orifice of the duct. Palate In the lamina propria of the hard palate and soft palate, three or four layers of veins form a well-developed venous plexus 100-800 pm in diameter (Fig. 11). Figure 12 depicts one of the numerous venous valves that are found in this plexus. In the dog palate, many transverse palatine ridges are distributed over almost the entire length of the hard palate. The capillary loops in the papillae of these ridges form regular rows that are aligned at a right angle to the curved ridges, a s shown in Figure 13. Most of the capillaries in the palatine ridges take the shape of simple hairpin loops (Fig. 14). However, in the crest of the ridges, the capillaries form complex loops with many anastomoses (Fig. 15). As compared with the hard palate, the mucous membrane of the soft palate is more highly vascularized and the papillae of the lamina propria are shorter and fewer in number. As in the hard palate, the capillary loops in the papillae are aligned in parallel rows that extend from the gingival region of the palate to the palatine raphe. The morphology of these capillary loops, as shown in Figure 16, is similar to those of the buccal mucosa (Fig. 8) and hard palate (Fig. 14). Many excretory ducts of palatine glands open onto the soft palate. Capillary loops encircle the orifice of these ducts and form complex anastomoses in a corollalike network (Fig. 17). Dorsal Lingual Mucosa In describing the vasculature of the lingual papillae, one is faced with a problem of terminology. Each lingual papilla is covered by epithelium and contains a core of connective tissue, the papillae of the lamina propria. In this paper the term papilla is used to denote the lingual papillae as well a s the connective tissue papilla that they contain. Examination of the vascular casts revealed that, in the dorsal lingual mucosa, branches from arteries and veins in the submucosa enter the lamina propria and form a subpapillary vascular network. From this network capillaries extend into the papillae. The subpapillary network consists of two layers of vessels. By removing the capillary loops in the papillae, the two layers of vessels could be visualized. The vascular network just beneath the papillae is composed of small arterioles and venules. The second Fig. 25. External view of vascular network in a vallate papilla (VP) and encircling ridge (large white arrow). Arrowheads, capillary loops in secondary papilla (11); asterisks, unvascularized area. Bar = 100 wn. layer, located just beneath the first layer, is composed of larger venules and arterioles. The casts of the largest of these venules had a diameter of 160 km, whereas the diameters of casts of the arterioles reached a maximum of 50 km. Many descending limbs from capillary loops in the papillae drain into the larger venules in this layer. Capillary loops are distributed throughout the papillae within the lingual papillae, as shown in Figure 18. The capillary loops in the individual papillae are connected to capillary loops in adjacent papillae by a subpapillary capillary network (SPCN) consisting of a single layer of capillaries running just beneath the epithelium. Filiform Papillae Of the lingual papillae, the filiform papillae are the most numerous. They are located on the rostrodorsal two-thirds of the tongue and consist of cone-shaped, fine, pointed structures composed of a core of connective tissue that carries secondary and tertiary papillae having the appearance of coiled loops. Capillary loops were found only in the primary papillae. In general, the capillary loops in the filiform papillae are arranged radially beneath the surface epithelium in a corolla-like pattern, with the largest primary capillary loop always near the lingual side of the papilla, a s shown in Figure 19. The primary capillary loop is surrounded by one to two secondary loops and three to five tertiary loops located on each side of the papilla. In the primary capillary loops, several ascending limbs follow a course toward the filiform papilla, then branch off and anastomose with adjacent ascending and descending loops, finally converging into a large descending limb that appears to drain directly into one of the small venules of the outer vascular layer of the subpapillary vascular network. Tertiary capillary loops are formed of one ascending limb (an arterial capillary) and one descending limb (a venular capillary). These loops conform to a very simple hairpin pattern. In contrast to this, secondary capillary loops are found to be intermediate in type between primary and tertiary loops. These loops form fewer anastomoses than do the primary loops. Fungiform Papillae Mushroom-shaped fungiform papillae are interspersed among the filiform papillae. Taste buds are present on the dorsal surface of these papillae. Because of their rich capillary network, these papillae appear as reddish prominences. The capillary loops of the fungiform papillae conform to the mushroom shape of the papillae. The capillaries entering the base of each papilla are arranged radially and contain many complex anastomoses. Several ascending limbs of these capillaries form short, hairpin loops in the superficial portion of the connective tissue papilla, a s shown in Figures 20 and 21. Immediately subjacent to this capillary network, the ascending roots converge into a few descending limbs, pass downward to the base of the papilla, and then drain into small venules in the subpapillary vascular network. 458 Y. KISHI ET AL. Foliate Papillae The foliate papillae are mucosal folds that occur on the dorsolateral margins of the tongue, rostral to the palatoglossal arch. These papillae are also associated with taste receptors. There are 8 to 12 foliate papillae that consist of parallel clefts that are bounded by narrow folds of the mucous membrane. Each papilla appears long and slender and is aligned at a right angle to the dorsal surface of the tongue (Fig. 22). Figure 23 depicts a portion of the vascular network in a foliate papilla. Within the network can be seen a large venule 100-120 pm in diameter and a n arteriole 35-40 pm in diameter. The arteriole follows a course that is parallel to, and just beneath, the epithelia1 lining of the foliate papilla. Capillary branches enter the papilla and form either a flat capillary network, with a meshwork approximately 50 pm in diameter, or small hairpin loops that extend into the superficial layer of the papilla. These capillaries anastomose with each other and converge into a large venule such a s the one shown in Figures 22 and 23. Between foliate papillae, the SPCN is similar to the capillary network within the papilla. However, neither arterioles nor venules could be identified beneath the SPCN between the papillae. avascular areas could be observed among these capillaries. On the sides of these avascular areas, capillaries are arranged in a flat network. Encircling each vallate papilla are one or two vascular prominences, the outer layers of which are formed either by a flat capillary network or by small hairpin loops. DISCUSSION The corrosive resin cast technique provides a n ideal method for studying three-dimensional images of the microvascular network of tissues. As compared with other vascular perfusion methods, this technique offers several advantages. The ability to obtain imprints of the walls of small blood vessels makes it possible to differentiate between arterioles and venules. Thus, in the walls of arterioles, the resin cast impressions of endothelial cells are spindle-shaped whereas in venules they have a hexagonal appearance (Kish e t al., 1988). In this study the resin cast method used in previous investigations was modified and improved by injecting Mercox into vessels that had first been fixed with glutaraldehyde. In this way we were better able to preserve the walls of blood vessels and prevent the extravasation of resin. The use of a fixative is also designed to minimize the expansion of vessels during Conical Papillae injection of the resin, thus making it possible to obtain In the dog, the conical papillae are distributed in the accurate estimates of the size of vessels. caudal portion of the tongue. They are the tallest of the Our results indicate that in the dog oral mucosa the lingual papillae and are shaped like a double convex configuration of capillary loops within each papilla is lense. determined by the shape of the papilla. In general, the Several arterioles pass upward from the mucosa and shape of the capillary loops in the papillae of gingiva, enter each papilla. These branch to form a capillary buccal mucosa, and hard and soft palate resembles a network in the superficial layer of the papilla. The hairpin. This is in agreement with the results of a prelower half of this network is flat while the upper half is vious study on the capillary system in the gingiva composed of many short hairpin loops (Fig. 24). A well- (Forsslund, 1959). Capillaries encircling the orifices of developed venular limb is situated in the deep layer of both small and large salivary glands form complex this capillary network. Many venules are arranged loops that anastomose with each other to form a coaround the center of the papilla. These anastomose and rolla-like pattern. (Figs. 13, 14, 21). finally converge into a large descending venule, the The form of the subpapillary vacular network located diameter of which measures 100 pm, where it reaches in the base of the papillae of the lamina propria was the base of the connective tissue papilla. Several small consistent in the various tissues examined. However, corolla-shaped capillary loops arise from near the base differences were noted in the density and extent of the of the papilla. These are similar in appearance to the vascular network. Thus the venous plexus was more capillary network encircling the orifice of the excretory highly developed in the masticatory mucosa of the hard ducts of small salivary glands in the buccal mucosa. palate and gingiva than in the other areas of the oral mucosa. Vallafe Papillae Venous valves were observed only in the lamina proThe vallate papillae, four to six in number, are the pria of the hard and soft palate and tongue. The preslargest of the lingual papillae. They are arranged in a ence of venous valves in the tongue has not been preV shape on the dorsal surface of the tongue and demar- viously reported. Klotz (1887) expressed the view that cate the junction of the rostral two-thirds and caudal it is not possible to visualize venous valves with diamone-third of the tongue. Each papilla is bounded by a eters that are less than 1 mm. More recently, Todo (1950) reported finding mesenteric venous valves havdeep circular furrow, the vallate papilla moat. In the lamina propria a t the base of each of the val- ing a diameter of only 40-200 pm. The casts of many of late papillae a n arteriole and venule run together the venous valves observed in the present investigation along a n annular course that follows the profile of the were considerably less than 1 mm in diameter (Fig. 12). In the palate the presence of venous valves may propapilla and circular ridge. From these vessels many branches pass into both the papilla and the ridge, thus vide a mechanism to prevent blood from being forced in forming a characteristic vascular network. Many small a direction away from the heart when strong masticatufts of hairpin-shaped capillary loops are arranged on tory forces compress the mucosa. High pressures may the superficial portion of each papilla (Fig. 25). Slightly also be created during movements of the tongue, and it larger capillary loops were observed in the secondary is likely that the venous valves help to control blood papillae on the dorsal surface of the papilla. Several flow by allowing blood to move in only one direction. VASCULAR NETWORK O F ORAL MUCOSA LITERATURE CITED Egelberg, J . 1966 The blood vessels of the dento-gingival junction. J . Periodont. Res., 1:163-179. Forsslund, G. 1959 The structure and function of the capillary system in the gingiva in man. Acta Odont. Scand. (Suppl. 26) 17r1-144. Hellekant, G. 1971 Circulation of the tongue. In: N. Emmelin and Y. Zotterman, eds. Oral Physiology. Proceedings of the International Symposium Held in Wenner-Gren Center, Stockholm, August 1971, Oxford, Pergamon Press, pp. 127-137. Hock, J., and K. Nuki 1971 A vital microscopy study of the morphology of normal and inflamed gingiva. J. Periodont. Res., 631-88. Kindlova, M. 1965 The blood supply of the marginal periodontium in Macacus Rhesus. Arch. Oral Biol., 1Or869-874. Kishi, Y. 1982 The development of the vascular network under the inner epithelium of the dog gingiva using resin casts and scanning electron microscopy. Jpn. J. Oral Biol., 24~706-726. Kishi, Y., S. So, and K. Takahashi 1988 Three-dimensional SEM 459 study of arteriovenous anastomoses in the dog’s tongue using corrosive resin casts. Acta Anat., 132r17-27. Kishi, Y., and K. Takahashi 1978 Scanning electron microscopy of the vascular architecture of the free gingiva. Jpn. J . Oral Biol., 20: 406-420. Klotz, K. 1887 Untersuhungen uber die vena saphena magna beim Menschen, besonders rucksichtlich ihrer klappenverhaltnisse. Arch. Anat. Physiol. Anat. Abtlg., 13r159-173. Swindle, P.F., and W.P. Maher 1963 Mucosal blood vessels of the palate. Dent. Prog., 3r106-111. 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