The Rete Mirabile of the Maxillary Artery in the Lion (Panthera Leo)

Home , Buccal artery, Inferior alveolar artery, Lacrimal artery, Masseteric artery, Maxillary artery

Okajimas Folia Anat. Jpn., 71(1): 1-12, May, 1994

The Rete Mirabile of the Maxillary Artery in the Lion (Panthera leo)

Hsien-Ming HSIEH and Akimichi TAKEMURA

Department of Anatomy, Osaka Dental University 5-31, Otemae 1-chome, Chuo-ku, Osaka 540, Japan (Director: Prof. Yoshikuni OHTA)

-Received for Publication, January 24, 1994-

Key Words: Maxillary artery, Rete mirabile, Blood supply, Plastic injection, Lion

Summary: The afferent and efferent arterial branches of the maxillary rete were investigated in 4 lion (Panthera s. Felis leo) heads preserved in the author's department. The heads were injected with acryl plastic via the common carotid arteries to make corrosion casts of the carotid system, and examined from the standpoint of comparative anatomy. The following afferent arterial branches were observed. Medial retial branches from the maxillary artery, anterior retial branches from the anterior deep temporal artery and intraretial branches of the maxillary artery passing in the rete. The rete was constructed from the following arterial resources: Most of the lateral and inferior surfaces of the rete and deep part of the maxillary nerve tunnel from the intraretial branches; the posterior surface and posterior part of the lateral surface from the medial retial branches, and the anterosuperior part of the lateral surface from the anterior retial branches. Eight efferent arterial branches were observed. The external ethmoidal, lacrimal, interretial and anastomotic arteries, the extraocular muscular, meningeal and temporal muscular branches and the communicating branch with the external ethmoidal artery. The anastomotic artery was always well developed and played the role of the main supply route to the brain instead of the obliterated internal carotid artery as observed in the cat. Unlike that of the cat, however, the maxillary artery of the lion always passed lateral to the pterygoideus lateralis muscle, and the lateral part of the rete was not constructed because there were no lateral retial branches such as those observed in the cat.

The first description of the carotid system of the Materials and Methods Felis domestica (s. Felis catus) was presented by Tandler in 1899. Since then, the external and internal Four young lion (Panthera s. Felis leo) heads carotid systems in the felis family have been reported injected with acryl plastic into the carotid system, by several investigators. Recently, the existence of preserved in the Department of Anatomy, Osaka the rete mirabile, which is named the rete mirabile Dental University, were used for this study. The a. maxillaris, has been confirmed. This rete is observed acryl plastic was injected via the common carotid as a large-scale arterial plexus intertwined with a arteries by means of the plastic injection method venous plexus, but an adequate explanation of its (Taniguchi, Ohta et al., 1952, 1955). Six of these functional significance has not been given. lairlimann injected heads were treated with 20% sodium (1913) and Takemura (1982) carried out detailed hydroxide to digest soft tissues and prepare corrosion observations on the vascularization of the rete, and casts of the carotid system. The remaining two sides its afferent and efferent arterial branches in the were preserved in 10% formalin solution to prepare domestic cat. Takemura elucidated that the anasto- dissection specimens. These materials were used for motic artery diverging from the rete supplied a large observation and measurement of the rete and maxil- amount of blood to the brain instead of the obliter- lary artery. ated internal carotid artery. There have been few reports on the gross angiology of the giant cat family (Panthera). The facial artery of the lion was described Findings by Lin et al. (1990), the arterial supply of the lion masseter muscle by Matsushita et al. (1992) and the Maxillary artery: ramifications of the external carotid artery in the lion This artery (7.0 mm in diameter), a continuation by Takemura et al. (1992). The present authors of the external carotid artery as a main vessel, curved attempted to investigate the rete mirabile of the anteromedially at the level of the mandibular angular maxillary artery, and its afferent and efferent arterial end 2/5 at the posterior margin of the mandibular branches utilizing plastic corrosion casts. We com- ramus. It finally gave rise to the masseteric artery pared the findings with those of the cat rete. (2.6 mm in diameter) and the posterior deep tern- 1 2 H-M. Hsieh and A. Takemura poral artery (2.0 mm in diameter) from its superior lateralis muscle and superior to the mandibular nerve wall, and after bending antero-supero-medially, gave (Figs. 2, 6), and gave rise to the middle meningeal rise to the inferior alveolar artery (2.5 mm in diam- artery (2.0 mm in diameter) posteromedially (Figs. 1, eter) from its anterior wall (Figs. 1, 5). However, 2, 8). The posterolateral end of the maxillary rete retial branches corresponding to the lateral retial was located just on the level of its point of origin. branch in the cat (Takemura 1982) from the middle The maxillary artery passed along the inferolateral and last arteries were not observed in any of the margin of the rete and bent anterolaterally toward 8 examples. The maxillary artery ran antero-supero- the anteroinferior end of the rete, where it gave rise medially on the lateral surface of the pterygoideus to the anterior deep temporal and zygomatic arteries

Fig. I. Lateral view of the maxillary rete of the left side. Schematic illustration of the rete and its vicinity. The mandible and the zygomatic arch were removed. The maxillary rete extends from the oval foramen to the optic canal surrounding the maxillary nerve. The maxillary artery passes along the inferolateral margin of the rete.

Key to Abbreviations in Figs. 1 and 2

aa : Anastomotic artery mx : Maxillary artery ad : Anterior deep temporal artery ob : Extraocular muscular branch ar : Anterior retial branch pd : Posterior deep temporal artery bn : Buccal nerve rm : Anastomotic ramus between the middle ee : External ethmoidal artery meningeal and anastomotic arteries eo : External ophthalmic artery za : Zygomatic artery ia : Inferior alveolar artery C : Condyle of mandible ic : Internal carotid artery G : Trigeminal ganglion if : Inferior alveolar nerve L : Pterygoideus lateralis muscle ir1 : Superior intraretial branch MD : Mandibular nerve lb : Lingual branch MX : Maxillary nerve ln : Lingual nerve O : Ophthalmic nerve ma Masseteric artery R : Rete mirabile of the maxillary artery mm : Middle meningeal artery Arrow : Direction of snout The Rete Mirabile of the Maxillary Artery in the Lion 3

Fig. 2. Superior view of the maxillary rete of the left side. Schematic illustration of the rete and its vicinity. Part of the sphenoid bone and the mandibular fossa were removed. The maxillary artery passes lateral to the pterygoideus lateralis muscle. The maxillary nerve penetrates the maxillary rete.

(Figs. 2, 7). The maxillary nerve penetrated the rete middle meningeal artery in 7 of them (Fig. 1), and in anterolaterally from the middle of its posterior mar- the remaining case arose directly superomedially gin, in company with the maxillary artery in the from the superior wall of the maxillary artery at the anterior half of the rete, but they were not parallel to level of the origin of the middle meningeal artery each other. (Fig. 8). Ramifying repeatedly, it gave off branches to the superomedial that passed up to the antero- 1. Afferent arterial branches to the rete superior end of the rete, forming a ridge between its The medial, anterior retial and intraretial posterior and lateral surfaces, and finally became branches were observed as resources of component component arterial branches which formed the anas- arterial branches of the rete in the lion. The passage tomotic artery. Branches to the medial formed the of the maxillary artery was clearly visible from the posteroinferior margin and posterior surface of the lateral side because the above three retial branches rete and the posterior wall of the maxillary nerve did not surround this artery but passed medially. tunnel (named in the cat by Takemura 1982), which 1) Medial retial branches (in the cat by Takemura perforated the rete as an arterial-mesh cylinder sur- 1982) rounding the maxillary nerve. These were observed as the superomedial and (b) Inferomedial retial branch (in the cat by inferomedial retial branches. The former was seen in Takemura 1982) (Figs. 5, 8) all 8 examples observed and the latter in only 2 of This branch was seen in only 2 of the 8 examples them. observed. In one of the two cases, it arose antero- (a) Superomedial retial branch (in the cat by medially from the inferomedial wall of the maxillary Takemura 1982) (Figs. 1, 5, 8, 9) artery, proximal to the origin of the superomedial This branch (1.0 mm in diameter), seen in all 8 retial branch and distal to the origin of the posterior examples observed, arose medially from the medial deep temporal artery (Fig. 8). In the other cases it wall of the maxillary artery in common with the arose in common with the lingual branch from the 4 H-M. Hsieh and A. Takemura

maxillary artery (Fig. 5). This branch reached the perior, and posteromedial. Only the last was located inferoposterior part of the rete by passing along the in the cranial cavity. The whole rete appeared as a inferomedial to the maxillary artery for a short dis- type of trigonal pyramid, the top of which was the tance, where it constructed the posterior foramen anterosuperior corner and the base of which was and wall of the maxillary nerve tunnel. In the 6 cases formed by the inferior surface of the rete. The in which this branch was defective (Fig. 13), it was posterior surface was flat, in close contact with the supplemented by a branch passing medially from the cranial bone, but the anteromedial surface was con- superomedial retial branch. cave, in close contact with the orbital muscular 2) Intraretial branches (in the cat by Takemura pyramid. The maxillary artery penetrated the rete in 1982) a medial arc from the posterolateral corner to the These branches, six to eight in number in each anteroinferior corner, and was located by itself on of the 8 examples observed, were afferent retial the inferolateral margin of the rete. In other words, branches which arose directly from the maxillary its lateral side was not surrounded by component artery passing along the inferolateral margin of the arterial branches of the rete in any cases observed, rete. They could be divided into superior and inferior but was exposed laterally. The maxillary nerve pen- intraretial branches according to their origin on the etrated the rete from its posterior margin to its maxillary artery. anteroinferior corner, where it passed anteriorly and (a) Superior intraretial branches (in the cat by slightly laterally, medial to the maxillary artery. Takemura 1982) (Figs. 1, 7, 9, 11) Accordingly, the maxillary nerve tunnel was formed These branches (0.8-2.0 mm in diameter), num- as an arterial-mesh cylinder surrounding the maxillary bered 3 to 5 in each of the 8 examples observed. artery in the rete. Arterial component branches They arose medially from the superior wall of (M. 1.0 mm in diameter) were coiled with numerous the maxillary artery when it ran along the infero- venous branches which formed a pterygoid venous lateral margin of the rete. Among them, the middle plexus (Fig. 12) that did not extend beyond the rete. branches were largest (Fig. 7), and the proximal branches inclined forward and the distal branches 3. Efferent arterial branches of the rete backward.They ramified and became the anas- The anastomotic, external ethmoid, lacrimal and tomotic artery after it formed the lateral surface interretial arteries and the extraocular muscular, of the rete, core and the superior wall of the maxil- meningeal and temporal muscular branches and com- lary nerve tunnel. municating branch with the external ethmoidal (b) Inferior intraretial branches (in the cat by artery, were observed as efferent arterial branches Takemura 1982) (Figs. 9, 12, 13) of the rete. These branches (0.5-1.2 mm in diameter), 1) Anastomotic artery (in the cat by Takemura numbered three to four in each of the 8 examples 1982) (Figs. 1, 2, 10, 11, 13) observed, arose downward from the inferior wall of This artery (0.8-3.0 mm in diameter) was fairly the maxillary artery when it passed along the infero- well developed in all 8 examples observed. It was lateral margin of the rete (Fig. 13). They immediately formed by 6-9 component arterial branches of the bent medially, ramifying frequently, and formed the anterosuperior part of the rete and a ridge between inferior part of the rete and the inferior wall of the its posterior and anteromedial surfaces. These com- maxillary nerve tunnel. Most of them became the ponent branches could be composed of two groups, anastomotic artery and partly the interretial artery. posterosuperior and anteroinferior. The former was 3) Anterior retial branches (in the cat by derived from branches of the lateral and posterior Takemura 1982) (Figs. 7, 9) surfaces of the rete (Fig. 10) and the latter from These branches (0.5-1.2 mm in diameter), num- those of the inferior and anteromedial surfaces (Fig. bered two to four in each of the 8 examples observed, 13). Both groups passed posteromedially through arose backward from the posterior wall of the the orbital fissure and entered the cranial cavity anterior deep temporal artery at the anterior margin in company with the oculomotor, trochreal and of the rete (Figs. 7, 9). Ramifying frequently, they abductor nerves. Numerous branches of both groups became the anastomotic artery after forming the gradually decreased in number by anastomosing with anterior margin and the anterior 1/3 of the lateral each other and immediately were collected into the surface of the rete. anastomotic attery (Fig. 13), which received Willis' cerebral arterial ring via a rudimentary, intracranial 2. Structure of the rete segment of the internal carotid artery (Figs. 2, 15). The rete of the lion had four surfaces; the posterior, Immediately before collection, the anastomotic artery lateral, inferior and anteromedial, and four corners; received an anastomotic branch of the middle men- the posterolateral, the anteroinferior, anterosu- ingeal artery (Fig. 2). The Rete Mirabile of the Maxillary Artery in the Lion 5

2) External ethmoidal artery (in the cat by Shimizu 7) Communicating branch with the external eth- 1968) (Figs. 1, 2, 6, 10) moidal artery (in the cat by Takemura 1982) This artery (2.2 mm in diameter), seen in all (Fig. 14) 8 examples observed, was formed by 2-5 component This branch (1.2 mm in diameter), seen in all 8 branches in the anterosuperior corner of the rete. It examples observed, arose via a common trunk with penetrated upward to the orbital membrane and the interretial artery, left the trunk about 10 mm curved forward superior to the levator palpebrae distal to the origin of this artery and anastomosed superioris muscle, receiving communicating branches with the external ethmoidal artery after passing from the anteromedial part of the rete immediately tortuously medial to the extraocular muscular before entering the ethmoidal foramen (Fig. 14). pyramid. 3) Extraocular muscular branches (in the cat by 8) Temporal muscular branch (in the cat by Takemura 1982) (Figs. 9, 10, 12) Takemura 1982) (Fig. 10) These branches (0.5 mm in diameter) numbered This branch (1.5 mm in diameter), numbered one 3-5 in each of the 8 examples observed. Two or or rarely two in all 8 examples observed, was foaned three of them arose anterolaterally from component by several component branches of the posterolateral branches of the anterior margin of the lateral surface corner of the rete or the posterior part of the postero- of the rete, and the others from the anteromedial superior margin of the lateral surface, and supplied surface of the rete. These muscular branches pen- the temporalis muscle. etrated the orbital membrane to supply the extraocular muscles. 4. Arteries diverging from the maxillary artery in or 4) Meningeal branch (in the cat by Takemura near the rete 1982) (Fig. 10) 1) Middle meningeal artery (Figs. 2, 8) One meningeal branch (0.8 mm in diameter) was This artery (2.0 mm in diameter) was seen in all 8 seen in each of the 8 examples observed. In 7 cases, examples observed. It arose medially and slightly it arose posteromedially from component branches posteriorly from the medial wall of the maxillary of the posterior surface of the rete near the antero- artery at a location where this artery passed across superior corner (Fig. 10) and immediately entered the mandibular nerve. It passed posteromedially the cranial cavity through a small foramen in a medial to the posterior margin of the rete to enter suture between the major and minor alae. It curved the cranial cavity via the oval foramen. It bent laterally along the suture to supply the dura of the backward on the dura after giving off a communicat- middle cranial cavity. In the remaining one case, it ing branch with the anastomotic artery. diverged posterosuperiorly from the superior wall of 2) Lingual branch (Figs. 5, 8) the anastomotic artery just before it became one This branch (1.2 mm in diameter) was seen in all 8 channel and curved antero-supero-laterally to supply examples observed. It arose from the middle nrienin- the dura mentioned above. geal artery in 7 cases and from the inferomedial 5) Lacrimal artery (Figs. 10, 12) retial branch in one case. It passed anteroinferiorly This artery (0.6 mm in diameter), seen in all 8 medial to the pterygoideus medialismuscle and infero- examples observed, was formed by 2 or 3 component lateral to the lingual nerve, and finally reached the branches of the anteroinferior corner of the rete. It floor of the mouth, giving off 2-4 medial pterygoid left the anterior margin of the rete anterosuperiorly muscular branches. and passed tortuously along this margin up to the 3) External ophthalmic artery (Figs. 9, 10, 11, 12) anterosuperior corner to supply the lacrimal gland. This artery (2.0 mm in diameter) was seen in all 8 6) Interretial artery (in the cat by Takemura 1982) examples observed. It arose superomedially from (Figs. 10, 12, 13, 14, 15) the maxillary artery, and had no communication This artery (1.6 mm in diameter), seen in all 8 with component branches of the rete, and passed examples observed, was formed by several com- tortuously anterosuperiorly up to the eye-ball via the ponents branches that protruded anteriorly from the anterosuperior corner of the rete. anteromedial part of the inferior surface of the rete 4) Anterior deep temporal artery (Figs. 1, 2, 7, 9) and made a common trunk with a communicating This artery (2.0 mm in diameter), seen in all 8 branch of the external ethmoidal artery (Fig. 14). It examples observed, arose upward from the maxil- passed posteromedially beneath the optic nerve along lary artery at a position immediately distal or at the the inferomedial wall of the optic canal to enter the anteroinferior corner of the rete. It passed upward cranial cavity. It anastomosed with the opposite along the anterolateral margin of the rete up to the fellow beneath the optic chiasma and passed for- anterosuperior corner of the rete. En route it gave ward as a communicating branch with the internal twigs to the temporalis muscle. ethmoidal artery impar (Figs. 10, 15). 6 H-M. Hsieh and A. Takemura

5) Zygomatic artery (Figs. 7, 9) A clear difference in the topographical relation This artery (0.8 mm in diameter) was seen in all 8 between the maxillary artery and rete is found in the examples observed. It arose superoanteriorly from course of this artery, that is, the maxillary artery the superior wall of the maxillary artery at a position passes medial to the pterygoideus lateralis muscle in distal to the origin of the anterior deep temporal the cat but lateral to it in the lion. This relation lends artery and passed up to the zygomatic process of the significance to topographical structures in the ptery- maxilla to supply the temporalis muscle. It rarely goid region, such as the pterygoideus lateralis muscle gave rise to 1 or 2 anterior retial branches backward. and blood vessels around it (Fig. 3). 6) Buccal artery Takemura (1982) described four afferent arterial This artery (2.0 mm in diameter), seen in all 8 branches in the cat, the lateral, medial, anterior examples observed, arose superolaterally from the retial and intraretial branches. The lateral retial superolateral wall of the maxillary artery at a position branch of the cat always passed lateral to the above 30-50 mm distal to the rete and gave twigs to the muscle up to the rete. However, this branch in the anterior part of the masseter muscle (Matsushita, lion is defective, and only the other three branches 1992) and buccal mucosa. It did not communicate were recognized in the cases studied. Why is the with retial branches. lateral retial branch defective in the lion? Examining the human fetus, Padget (1948) stated that the maxillary artery in the early fetal stage was constructed by Discussion two routes holding the pterygoideus lateralis muscle between them and that either route may disappear in 1. Review of literature on the rete mirabile of the later developmental stages. Saito (1988) studied the cat family ramifications of the posterior deep temporal artery Previous investigations on the angiology of the in the cat, and found that the lateral retial branch domestic cat (Felis catus) head have elucidated: was really the maxillary artery itself judging from its Entire obliteration of the internal carotid artery, the passage and ramifications. Thus the maxillary artery existence of the rete mirabile of the maxillary artery was composed of two routes, between which the and the divergence of arterial vessels supplying the pterygoideus lateralis muscle was held, in many cats. brain from the rete as a group of efferent arterial Based on the above investigations, the two routes of routes (Fig. 4). Reports have questioned whether the maxillary artery built up in the early developmen- this arterial rete is observed in all species of the felis tal stage of the cat do not disappear; one may remain family. There have been many surveys of the rete in as the lateral retial branch on the lateral side of the the domestic cat, but few in the giant cat family pterygoideus lateralis muscle and the other develops (Panthera), including the lion, and tiger. Previously, to form the maxillary artery on its medial side. Tandler (1899) reported the existence of the rete However, in the lion, the medial route disappears, mirabile both in the tiger (P. tigris) and leopard and the lateral route remains as the maxillary artery. (P. parilus). Davis and Story (1943) described the Finally, one of the afferent arteries to the rete does carotid circulation of the cat, lion and leopard, and not exist in the lion. pointed out a small-scalerete mirabile and an isthmus The pterygoideus lateralis muscle does not develop of the internal carotid artery in the lion and leopard. in either the dog or cat families because it may be Takemura et al. (1992) elucidated a well-developed not necessary to perform a grinding movement of rete on the maxillary artery of the lion, like that seen the temporomandibular joint. Nevertheless, this in the domestic cat, and since the internal carotid muscle (only 10 mm in diameter) of the lion arises artery was not completely obliterated, but degener- from the external pterygoid fossa (which has a short ated, this vessel did not play a role as a nutrient vertical dimension) of the anterior sphenoid bone vessel to the brain. and makes an insertion at the pterygoid fossa of the From the literature, it can be concluded that the medial end of the condylar process of the mandible existence of the rete has been confirmed in the after passing postero-infero-laterally across and domestic cat of the felis family as well as in the tiger above the buccal nerve. In the cat, this muscle arises and leopard of the giant cat family. The existence of from a position lateral to the pterygoid process and a well-developed rete mirabile was also ascertained passes laterally across and beneath the nerve. In the in the present study; thus the rete seems to be human subject, the buccal nerve passes between the formed in the maxillary artery of all species of the upper and lower heads of this muscle, since the cat family (Fig. 4). vertical distance of this muscle origin is fairly great. In conclusion, only the lower head may remain in 2. Correlation between the maxillary artery and the cat and the upper head in the lion. afferent arterial branches of the rete An important branch composing the rete in the The Rete Mirabile of the Maxillary Artery in the Lion 7

Fig.3. Superior view of the maxillary rete of the left side. Fig. 3a. Cat (Fells catus), cited from Takemura, 1982. Fig. 3b. Lion (Panthera leo), a reduction of Fig. 2. The maxillary artery of the lion passes lateral to the pterygoideus lateralis muscle, but it in the cat passes medial to the muscle. bn: Buccal nerve, mx: maxillary artery, C: condyle of mandible, L: pterygoideus lateralis muscle, VI : ophthalmic nerve, V2: maxillary nerve, V3: mandibular nerve. cat is the lateral retial branch, since it is involved lion is not formed because the maxillary artery of in the composition of the rete and supplements the lion passes lateral to the pterygoideus lateralis branches that have defected. But this branch was muscle. Accordingly, the external aspect of the rete defective in all the lion samples we observed. The in the lion appears as a simple trigonal pyramid, medial and anterior retial branches are always under since the number of the ends and surfaces is less than developed than those of the cat in terms of their in the cat, while the posterolateral end of the rete is origin, number and composition of the rete. The covered by many of its component branches since it superior and inferior intraretial branches, however, is positioned just lateral to the maxillary artery. In are well developed and construct the lateral and contrast, the entire passage of the maxillary artery inferior surfaces of the rete and almost surround the is directly visible in the lion, since no component wall of the maxillary nerve tunnel. It can be said that branches diverge laterally from the maxillary artery the rete of the lion is composed of the intraretial and its passage corresponds to the lateral retial branch. branches. Consequently, the maxillary rete of the lion appears as a trigonal pyramid, the inferior surface of which is 3. Morphological aspect of the rete the base and the top of which is the anterosuperior The rete in the cat was reported by Tandler end, almost the same as that of the cat. (1899), Hiirlimann (1913) and Martinez (1967) to have the fouli of a pyramid with four corners. Takemura (1982) described a similar area in the cat Acknowledgments as the posterior corner where the maxillary artery and the medial retial branch passed the posterolateral The authors thank Prof. Yoshikuni Ohta for criti- corner built by the lateral retial branch, by which the cally reading this manuscript, and other staff members antero- and posterolateral parts were divided on the of the Department of Anatomy for their invaluable lateral surface. However, the posterior end in the assistance. 8 H-M. Hsieh and A. Takemura

This work was presented at the 35th Annual Mschr. Anat. Physiol, 191329:371-442. Meeting of the Japanese Association for Oral Biology 3) Lin R-T, Takemura A. The facial artery of the lion (Panthera leo). Okajimas Folia Anat. Jpn., 1990;66:417-432. in Nagasaki on 12 October 1993, and at the 99th 4) Martinez P. Sur la morphologie du reseau admirable extra- Meeting of the Japanese Association of Anatomists crdnien. Acta Anat., 1967;67:24-52. in Yamagata on 31 March 1994. 5) Matsushita J, Takemura A. Arterial supply of the masseter muscle in the lion (Parenthera leo). Okajimas Folia Anat. Jpn., 1992;69:157-168. Literature cited 6) Padget DH. Development of the cranial arteries in the human embryo. Contrib. Embryol., 1948;32:205-262. 1) Davis DD, Story HE. The carotid circulation in the domestic 7) Saito S. On the posterior deep temporal artery of the cat. cat. Zool. Series Field Mus. Nat. Hist. , 1943;28:1-47. Jpn. J. Oral Biol., 1988;30:277-292. (in Japanese) 2) Hiirlimann R. Die arteriellen Kopfgefasse der Katze. Intern. 8) Shimizu E. Stereological studies on several ducts and vessels

Explanation of Figures

Plate I

Fig. 4. The maxillary rete of the right side in the lion (4a) and of the left side in the cat (4b). Size comparison. xca. 1.8.

Fig. 5. Lateral view of the left side. The inferior alveolar, posterior deep temporal and masseteric arteries arise independently from the maxillary artery. The inferomedial retial branch (/') arises from the maxillary artery in common with the lingual branch, xca. 1.8.

Fig. 6. Superior view of the left side. Part of the sphenoid bone and the mandibular fossa were removed. The maxillary artery passes lateral to the pterygoideus lateralis muscle. The maxillay nerve penetrates the maxillary rete. xca. 1.

Fig. 7. Lateral view of the left side. The coronoid process and zygomatic arch were removed. The maxillary artery (mx) passes along the inferolateral margin of the rete. The superior intraretial branches (ir1) are largest in the middle. The lateral surface of the rete is formed by the superior intraretial and anterior retial branches (ar). xca. 1.5.

Fig. 8. Posterior view of the right side. In this case, the superomedial retial branch (mr1) arises from the superior wall of the maxillary artery. The inferomedial retial branch (mr2) arises from the inferior wall of the maxillary artery (mx). The middle meningeal artery (mm) arises from the maxillary artery in common with the lingual branch (lb) distal to the origin of the posterior deep temporal artery (pd). *:Posterior end of the maxillary nerve tunnel. xca. 1.8.

Fig. 9. Lateral view of the right side. In this case, three superior intraretial (iri) and three inferior intraretial (ir2) branches arise directly from the maxillary artery (mx), which is not covered with this artery. xca. 1.8.

Key to Abbreviations in Figures 4-15

aa : Anastomotic artery mx : Maxillary artery ad : Anterior deep temporal artery ob : Extraocular muscular branch ar Anterior retial branch pd : Posterior deep temporal artery bn : Buccal nerve re : Communicating branch between the rete ee : External ethmoidal artery and the external ethmoidal artery eo : External ophthalmic artery ri : Communicating branch between the inter- ia : Inferior alveolar artery retial and internal ethmoidal arteries ic : Internal carotid artery rm : Anastomotic ramus between the middle in : Interretial artery - meningeal and anastomotic arteries iri : Superior intraretial branch tb : Temporal muscular branch ir2 : Inferior interretial branch za : Zygomatic artery la : Lacrimal artery C : Condyle of mandible lb : Lingual branch G : Trigeminal ganglion ma : Masseteric artery L : Pterygoideus lateralis muscle mb : Meningeal branch arising from the rete MD : Mandibular nerve mm : Middle meningeal artery MX : Maxillary nerve mr : Medial retial branch O : Ophthalmic nerve : Superomedial retial branch R : Rete mirabile of the maxillary artery mr2 : Inferomcdial retial branch Arrow : Direction of snout The Rete Mirabile of the Maxillary Artery in the Lion 9

Plate I 10 H-M. Hsieh and A. Takemura

by injection method of acrylic resin. XX. On the ethmoidal 11) Tandler J. Zur vergleichenden Anatomic der Kopfarterien artery in some mammals. Okajimas Folia Anat. Jpn., 1968; bei den Mammalia. Denkschr. Kais. Akad. Wiss. Mathema- 45:99-141. tisch-naturw. Klasse, Wien, 1899;67:712-716. 9) Takemura A. The rete mirabile of the maxillary artery in the 12) Taniguchi Y, Ohta Y, Tajiri S. New improved method for cat. Okajimas Folia Anat. Jpn., 1982; 59:103-136. injection of acrylic resin. Okajimas Folia Anat. Jpn., 1952; 10) Takemura A, Okuda H, Okada S. Toda I, Ohta Y. Ramifi- 24:259-267. cations of the external carotid system of the lion (Panthera 13) Taniguchi Y, Ohta Y, Tajiri H, Okano H, Hanai H. Sup- leo). Jpn. J. Oral Biol., (abstract) 1992; 34(suppl.): 173. (in plement to new improved method for injection of acrylic Japanese) resin. Okajimas Folia Anat. Jpn., 1955;27:401-406.

Plate II

Fig. 10. Postero-supero-medial view of the left side. The anastomotic artery (aa) arises from the anterosuperior part of the rete. The meningeal branch (mb) arises from the posterior surface of the rete. The interretial artery (in) anastomoses with the opposite fellow and passes forward as a communicating branch with the internal ethmoidal artery impar (ri). xca. 1.

Fig. 11. Superior view of the right side. The external ethmoidal artery (ee) and the external ophthalmic artery (eo) arise from the anterosuperior corner of the rete. xca. 1.5.

Fig. 12. Anterior view of the right side. The lacrimal artery (la) arises from the anterior margin of the rete anterosuperiorly. Arterial component branches are coiled with venous branches. *:Distal end of the maxillary nerve tunnel. Xca. 1.8.

Fig. 13. Inferior view of the right side. In this case, the inferomedial retial branch is defective. The inferior intraretial branches (ir2) arise from the inferior wall of the maxillary artery (mx) and form the inferior surface of the rete. Component branches of the inferior surface become the interretial artery (in) and the anastomotic artery (aa). The latter flows into one (f—). xca. 1.3.

Fig. 14. Inferomedial view of the right side. The comniunicating branch (re) with the external ethmoidal artery arises via a common trunk with the interretial artery (in) and communicates with the external ethmoidal artery (ee). xca. 2.5.

Fig. 15. Superior view of the retes on both sides. The interretial artery (in) anastomoses with the opposite fellow and passes forward as a communicating branch with the internal ethmoidal artery impar (ri). Arrowheads: Rudimentary, internal carotid artery, W: Willis' cerebral arterial ring. xca. 1.6. The Rete Mirabile of the Maxillary Artery in the Lion 11

Plate H