Lateral Pterygoid Muscle and the Temporomandibular Disc

Home , Lateral pterygoid muscle, Temporomandibular joint

David J,A, Heylings, BSc, MB This anatomic study examines the attachment of the lateral ptery- Lecturer in Anatomy goid muscle to the capsule and disc of the temporomandibular Queen's University of Belfast joint. The anatomy of the temporomandibular joint and its sur- School of Biornedical Science. roundings, in particular the insertion of the superior head of the Anatomy lateral pterygoid muscle, was studied by dissection and conven- Belfast, Northern Ireland tional histologie techniques. The material consisted of 16 cadaver IbL Nielsen, DDS specimens from individuals 60 years or older. The results showed Clinical Professor that only a part of the superior head of the lateral pterygoid muscle Department of Growth and is attached to the anterior portion of the capsule, which, in turn, is Development firmly attached to the disc, giving the impression that the muscle Charles McNeill, DDS and the disc are directly connected. Ail specimens showed attach- Clinical Professor ment of the superior head of the lateral pterygoid muscle to the Department of Restorative Dentistry anterior medial portion of the capsule, but they showed varying and Director degrees of attachment to the lateral aspect of the temporomandihu- Center for Temporomandibular lar joint capsule. The remaining part of the superior head of the Disorders and Orofacial Pain lateral pterygoid muscle attached to the mandibular condyle. Serial sectioning in no instance showed direct insertion into the disc of University of California. San Francisco the fibers of the superior head of the lateral pterygoid muscle. San Francisco, California J OROFACIAL PAIN 199S;9:9-16, Correspondence to: Dr David J,A, Heylings Queen's University of Belfast School of Biomédical Science, Anatomy Medical Biology Centre 97 Lishurn Road he anatomy of the temporomandibular joint (TMJ) has long Belfast BT9 7BL been the cause of debate nor only with respect to its role in the Northern Ireland Teriuiogy of joint pain, but also as ro wherher the superior head of the lateral ptcrygoid muscle (SLP) is atrached ro the disc or to the condyle of the mandible and contributes to disc displacement and joint pain. It is not in the scope of this paper to provide a compre- hensive review of the attachment of the lateral ptcrygoid, but rather to look, wirhout preconceived ideas, ar the artachmenr of rhe SLP, McDevitt' and Kaplan and AssaeP believed that the upper fibers of SLP are attached to the disc and capsule, especially to the medial aspect, and the lower fibers are blended with rhose of the inferior head and artached to the neck of the mandible. There are still, however, different camps of opinion; one believes that the SLP is not atrached ro the disc,'"' although a small proportion of the fibers are atrached to the anterior part of the capsule and hence are attached either directly or indirectly to the condyle and not the disc itself. The other camp describes the SLP as artached directly to the disc and the condyle.""" It is also believed rhat rhe SLP is atrached only to the anterior border of rhe capsule and to rhe disc." All invesrigators agree on rhe anrerior arrachment of rhe SLP to the periosteum of the infratemporal fossa lying on the greater wing of the sphenoid bone as far anteriorly as the infraorbiral fissure. Why this confusion exists is unclear because the studies involve both macroscopic and microscopic examinations of the muscle in relation to rhe joinr. According ro McDevitt' and Carpentier et al,'

Journal of Orofacial Pain 9 Heylings et al

there is a portion of the infratemporal fossa up to tissue inferior to the cranial base was sectioned m 10 mm anterior to rhe capsular attachment on the a transverse plane inferior to the floor of the max- base of the skull, where the mnscle does not attach illary antrnm. to the overlying periosteum. It is through this Ten of the 18 specimens were dissected in an space that the nerve to the masseter muscle and the identical tnanner. The dura marer was removed anterior and posterior deep temporal nerves pass.'' from the floor of the middle cranial fossa, and the The aim of this investigation was to determine foramen ovale and spinosum were clearly identi- the anatomic relationship hetween the lateral fied. The squamous part of the temporal bone was pterygoid muscle and the disc of the TMJ and to removed, ieaving the pericranium intact. discover if the muscle is attached directly to the Surrounding bone was then removed carefully, disc and/or to the capsule, as well as to the leaving the mandibular division of the trigeminal condyle of the mandible. In addition, this paper nerve and the middle meningeal artery intact. As looks at how the confusion in the literature might the dissection progressed, the condylar fossa was have developed- removed, leaving the pericranium intact. The pericranium was incised anterior to the stem of trigeminal nerve without damaging nerve or muscle. In Materials and Methods this way, the SLP, its attachments to the capsule of the TMJ, and any nerves lying superior to the lat- Eighteen specimens were collected, equal numbers eral pterygoid were exposed. Part of the muscle from the right and left sides of embalmed cadavers attached anteriorly to the cranial base was dam- of individuals aged 60 to 90 years used in the medi- aged slightly in the process. After recording all cal dissection room of the Department of Anatomy, findings, the pericranium superior ro rhe TMJ disc School of Biomédical Science, Queen's University, was incised. The disc was mobilized medially, pos- Belfast, Northern Ireland. Eleven of the specimens teriorly, and laterally. Next, the capsule was were from edentulous individuals, and seven speci- incised anteriorly where it was attached to the mens wete from individuals who had partial denti- mandibular condyle. The capsule was elevated, tions- The zygomatic arch had heen removed in all and the fibers of the lateral pterygoid muscle cases, and the ramus of the mandible had been sec- attached to this part of the capsule were teased tioned during the earlier dissection. apart to remove a specimen consisting of disc, In this stndy, three different approaches were attached capsule, and fibers of lateral pterygoid. used to examine the anatomy of the TMJ, The resultant specimen was then processed for 1. Gross dissection was performed on a tissue wax histology. block taken from the cranial skeleton that The other group of eight specimens was pro- included the middle cranial fossa superiorly cessed undissected for histologie sectioning- Due to and the inferior head of the lateral pterygoid the size of the blocks of tissue, six were cut in a muscle caudaily. Dissection was performed parasagittai plane on a microtome at a thickness of with a dtssection microscope to improve preci- 60 to 150 |am. Each section was serially mounted sion and to mmimize damage to the tissues. for examination after staining with one of the fol- 2- Histologie sections were made of identical lowing standard histologie stains: Masson stain undissected tissue blocks containing intact and Mallory's trichrome stain; alcian hine and van TMJ complexes, Geison's solution of trinitrophenol and acid 3, Histologie sectioning was performed on the dis- fuchsin; hematoxylin-eosin stain; or Weigart's eîas- sected specimens of disc, capsule, and muscle. tic stain,"'" The Masson stain and Mallory's trichrome stain were nsed for identification of During the removal of the tissue blocks, care muscle and collagen, the alcian blue and van was taken to ensure that previous dissection had Geison's solution for hyaline cartilage and colla- not damaged the disc or capsule and that it had gen, and the hematoxylin-eosin stain or the not progressed deep enough to expose the lateral Weigart's elastic stain to identify' elastic fibers- The pterygoid muscle. To remove the specimens, two final two specimens were split prior to histologie sections were made in the coronal plane: one pos- processing to ensure that the histologie sectioning terior to the external acoustic meatns, the other was performed parallel to the direction of the mus- anteriorly through the maxillary antrnm. The spec- cle fibers of the SLP, These sections were therefore imen was then released by sectioning through the in a plane angled approximately 26 degrees to the cranial base in a parasagittal plane just lateral to sagittal plane, and the sections were stained with the cavernous sinus to join the other two cuts. Soft Mallory's stain.

1O Volume 9, Nuniber 1, 1995 Fig 1 Supero lateral view of the left temporomandibular Fig 2 Supcrolateral view of the temporomandibular joint and lateral pterygoid muscle from a 75-year-old joint and lateral pterygoid muscle seen in Fig 1 with the maie. Superior surface of temporomandibular disc (D], temporomandibular disc reflecred superiorly and medi- internal carotid artery (IC), lateral pterygoid superior head ally, Superior surface of temporomandibular disc (D), (SL) and inferior head (IL), joint capsule cut (C), branch of internal carotid artery (IC), iateral pterygoid superior external carorid (EC). (Original magnification X 3.1 head (SL) and inferior head (IL), branch of external carotid (EC). (Original magnification X 3.)

Results similar fibers from the disc (Fig 3a), This was confirmed when whole joint complexes were viewed Lateral Pterygoid in the oblique, rather than sagittal, plane. While the majority of the SLP fibers were sectioned along The gross examination, later confirmed histologi- the length, the most cranial ones were not {Figs 3b cally, showed that only a part of the SLP was and 3c). From these figures, it is apparent that attached to the anterior part of the capsule, although a few of the most cranial fibers have con- which, in turn, was attached to the temporo- nections to the anterior aspect of the disc, most mandibular disc (Figs 1 and 2]. The size of this form tendinous bands reinforcing the anterior portion varied considerably from specimen to aspect of the capsule, and hence, the superior specimen. The remainder of the superior head was aspect of the condylar fovea. atrached to the condyle of rhe mandible. In all This arrangetnent is not obvious in the standard specimens, the muscle was clearly attached to the sagittal plane of sectioning (Fig 4). Studied seri- medial half of the anterior aspect of the capsule. ally, the sagittal plane of sectioning gives the Attachment to the lateral half of the anterior impression that the SLP attaches to the anterior aspect of the disc/capsule demonstrated a greater aspect of the disc even though the fibers have been degree of variability. In some cases no attachment sectioned. In this oblique plane, a triangular fold was observed. Other cases showed as much as two of the capsule, not seen in sagittal sections, is thirds of the fibers attached to the lateral aspect of between the inferior aspect of the disc and the the capsule. condyle. The tendons of the SLP are intimately The muscle was firmly adherent to the capsule associated with this fold, which could be a result as was the disc, giving the clear impression that of a forward displacement of the condyle prefixa- muscle and disc were directly connected (Fig 2). tion. Muscle fibers from the lateral pterygoid were To confirm this, several specimens selected at ran- attached to the mandible in a Iatninat fashion, dom were examined histologically. In no section blending with those from the SLP lying superior were muscle fibers clearly seen attached directly to and therefore closer to the TMJ than fibers from the disc in large numbers. The collagen bundles the inferior head. There appeared to be two dis- from the muscle passed into the capsule curving tinct muscles that shared a common area of inferiorly to blend with those of the capsule and attachment to the anterior of the mandible.

Journal of OrofacisI Pain 11 Heylings et al

Fig 3a Histologie section (100 |jm thick) of the speci- Fig .ib HiiUilogic stction (100 pni thick) from an 86- men in Fig 2. Temporomandibular disc (D), joint capsule year-old female. Temporomandibular disc {D¡, joint cut ends (C¡, and superior head of lateral pterygoid mus- capsule (C), superior lacerai pterygoid muscle (SL), infe- cle (SL). (Mallory's trichrome stain, original magnifica- rior lateral pterygoid muscle (IL). (Mallory's trichrome tion X 20.) stain, original magnification X 11.)

Fig 3c Higher magnification of histologie section ¡100 Fig 4 Histologie section of temporomandibular joint [im chick) shown in Fig 3b. Temporomandibulac disc ¡100 |.im thick) in a 72-year-old male. Temporomandib- (D), joint capsule (C), superior lateral pterygoid muscle ular disc {D¡, mandibular condylc (C), superior head of (SL], inferior lateral pterygoid muscle (IL]. (Mailory's lateral pterygoid muscle (LP), squamotympanic recess trichrome stain, original magnification X 23.) ¡ST], blood vessel in lateral prerygoid muscle (BV). ¡Masson stain, original magnificación X 10.)

Mandibular Nerve passed on the medial aspect of the lateral pterygoid muscle. In all specimens, a number of nerve branches were in the space posterior to the cratiial attachment of the lateral pterygoid and the base of the Other Observations skull. Usually three main nerve trunks were seen macroscopically ¡Eigs 5a and 5b), all radiating Both macroseopicaliy and histologically, numerous laterally from the foramen ovale. Tbe most ante- blood vessels were noted in the area, lying pre- rior trunk was at the lacerai aspect of the SLP no dominately posterior and slightly inferior to the further anteriorly from the anterior aspect of the condyle of the mandible. Several specimens capsule than the maximum anteroposterior dis- demonstrated a high degree of vascuiarity within tance of the TMJ space. The most posterior the lateral pterygoid muscle itself just anterior to branch was an average of 3 mm from the ante- the joint. The disc was attached posteriorly to the rior aspect of the joint capsule (range, 0 to I 0 squamorympanic fissure (Eig 4), and elastic fibers mm). These branches were in addition to the were within the tissues attached to the posterior main trunk of the mandibular division that edge of the disc.

12 Volume 9, Number 1, 1995 Heylings et al

Discussion

Our work supports the concept that on a macroscopic level, the superior fibers of the lateral pterygoid muscle appear to attach directly to the disc.'-'""'- On the microscopic level, however, the muscle fibers do not have their primary attachment directly to the disc but rather to the condylar fossa and the anterior aspect of the joint capsule. This supports the observations of several investiga- tors.*"'"''''" We found a firm adhesion between disc, capsule, and muscle—an arrangement that functionally allows them to act as an integral unit. Fig 5a Superior head uf the lateral ptecygoid muscle This finding is in agreement with the observations (SL) viewed from the middle cratiial fossa in a 70-year- of Okeson'" and others." Why has there been this old male, dissected in situ (before removal of tissue preponderance of differing reports? We believe tbis block). Trigeminal nerve and ganglion (TG), mandibular is a result of the approach to studying the TMJ division of tngeminal nerve and branches (M), internal structures. In studies that involve macroscopic carotid artery (IC), basilar artery (B¡, optic nerve (O), investigation, the SLP is observed to be attached to temporalis (T). (Original magnification X 2.) the disc, as was clearly seen in the present study. Unless these observations are followed up with a histologie section of the prepared muscle disc complex with the tendons attached directly to the capsule. It IS not observed that the tendons of the muscle fiber, as a rule, do not pass through to attach directly to the disc. On the other hand, histologie studies are usually performed with resultant sections in the sagittal, coronal, and horizontal planes. Using such an approach, it is impossible to include an intact muscle fiber passing all the way from the striated muscle fiber to the tendon to the ultimate point of attachment, a point also noted by Meyenberg et al.' In addition, most sections are thick, frequently in excess of 600 pm thick; therefore, histologie detail is extremely difficult to fol- low. We looked at sections with an average thickness of 100 pm. In the standard planes of sectioning, laterally we could report no attachment to the disc and capsule, and medially we could report that all of the SLP attached to the disc. This was in part due to being unaware of the frequent absence of the SLP attaching to the lateral aspect of the TMJ and being unable to trace a single fiber from muscle to point of attachment. The resultant interpretation, therefore, would be that the muscle fibers of SLP pass in three dimensions from the greater wings of the sphenoid: posteriorly, inferiorly, and laterally. There is no spiraling or twisting of the muscle fibers. It was only throtigh the axis parallel to rhe muscle fibers at approximately 16 degrees to tbe sagittal plane that such could he Fig 5b Superior head of the lateral pttrygoid mustie traced. (SL) viewed from the middle cranial fossa of an 86-year- old female. Mandibular division of tngeminal nerve (M) and branches (B), superior aspect of temporomandibular Functionally, however, it is important to include disc (D), ]oiiit capsule sectioned (C), floor of maxillary the observation that the SLP is firmly adherent to sinus (S), (Original magnification X 2.) the capsule, and hence the disc, medially. Laterally

Journal of Orofacial Pain 13 fHeylings et a¡

there is rhe attachment to the fascia of the masseter capsule itself. It has been suggested that they m^Y muscle.'"•"•="•=' From rhe attachment of the SLP it be involved in entrapment, but few authors seem could be deduced rhar ir would tend to pull the to consider this a possibility,*' One may speculate disc in an anterosuperomedial direction, thus that damage to muscle fibers of the "il '' would maintaining contact wirh the condylar fossa and result in swelling of the muscle, which < ""Id pos- the eminence on the base of rhe skull. The lateral sibly cause the muscle to press upward on the attachment to the masseter may reduce any medial nerve fibers. This pressure on the nerve could displacement of the disc. In effect, it would be result in loss of function, pam, or numbness, espe- expected to be active on closure as has been dem- cially when rhe condyle moves in an anterior direc- onstrated with elcctromyographic (EMG) stud- tion. Such a movement might furrher compromise ies.""-^' Even rhough the SLP muscle fibers are ori- the space for the nerves. In this project, it was not ented in an anteromedial direction, it is hard to possible to determine if rhe nerves were motor, sensory, or a combination, nor could the ultimate believe thar this would allow the disc in patients destination of these nerves be determined. with remporomandibular disorders to be displaced Although motor dysfunction should be easily in an anterior and medial direction since they also derecred clinically, sensory dysfunction, especially attach to the condyle. Perhaps its role is ro prevent proprioceptive loss, is not so readily discernible. the capsule and disc from moving posteriorly during closure, providing a rethering effect upon rhe disc and capsule during closing, and stabilizing the complex, as has been suggested by Tanaka as cited Conclusion by Okeson.'" Biomechanic analysis" and EMG studies of rhe The results of this gross anatomic and histologie SLP muscle have shown rhar rhis muscle is actively study of rhe TMJ anaromy supports the idea that involved during jaw closing,-'"™ and in clenching in the SLP does not attach directly into the disc, but retrudcd position of the mandible.'" It is possible rather to the anterior aspecr of the TMJ capsule. that rhe superior part of the muscle may he func- However, the firm connection between the capsule tioning nor as a primary closing and clenching and rhe disc ar this point strongly suggests that the muscle during retrusion, but instead as a srahiliz- muscle would conceivably influence tbe move- ing muscle for the mandible during rhese func- ments of the disc. The possible role of the SLP in rions. The muscle thus is active and builds tension displacement of the disc is still unknown and fur- as ir iengthens, stabilizing the disc/condyle com- ther research is needed. plex on closing. The lateral pterygoid muscle has been described as two muscles with an inferior head and a superior head with different functions,'•'-'''"'' The supe- Acknowledgments rior head is said to be involved in moving the mandible from side to side in the grinding process This research project was supported by a grant from the Craniomandibular Institute, Lafayecte, California, The Institute while keeping the teeth close together.'•''•"•'" The is a nonprofit organization dedicated to the education and inferior head instead functions to separate the research of craniomandibular disorders. The authors wish to teeth, such as when rhe mouth is opened, or to pull express rheir appreciation for the support of the Institute, the mandible to the contralateral side. It would seem important in the grinding process rhat the condyle and disc remain in close proximity, which References supports these functions of the muscle. It is con- ceivable thar the muscle pulls in a medial direction 1, McDevitt WE. Functional Anatomy of the Masticatory because the muscle fibers have no attachment to System, London: Butrerwortb, 1989, the lateral aspect of the disc. Instead, fihers from 2. Kaplan AS, Assael LA, Temporomandibniar Disorders; Diagnosis and Treatment, Philadelphia: WB Saunders the temporalis muscle are attached here.' 1951, Carpenrier et al,' however, found rhat the SLP 3, Mahan PE, Wilkinson TM, Gibbs CH, Mauderii A tends ro deflect the disc backward and upward, Brannon LS. Superior and inferior bellies of the lateral and they reported no independent action of the pterygoid muscle EMG activir>' at basic jaw positions I two heads of this muscle. ProsthetDent 19B3;50;710-718. 4. Pinkert R, The connection of the niusculus pterygoideus In our specimens, we observed several large lateralis to the discus acricularis and its importance for the nerves lying anterior ro rhe joint capsule. These movement in the temporomandibniar jomt. Zahn Mund nerves were frequently in direcr contact with the Kieferheilkd 1984;72:S53-558.

14 Volumes. Number 1, 1995 Heylirigs et al

Meyenberg K, Kubik S, Palla S. Relationships of the mus- 20, Sarnat BG, Laskin DM, Tbe temporomandibular joint: A cles of mastication to the articular disc uf the temporo- biological basis for clinical practice, ed 4. Philadelphia; mandibular joint, Helv Odour Acta 1986;30:815-834, we Saunders, 1992, Wilkinson TM. The relationship between the disk and che 21, Meyers LJ. Newly described muscle attachments to tbe lateral pterygoid muscle in the human temporomandibular anterior band of the articular disk of tbe temporo- joint, J Prosthet Dent 1988;60:715-724, mandibular joint, J Am Dent Assoc 1988;117:437-439, Wilkinson T, Chan EK, The anatcmic relationship of the 22, Juniper RP, Role of tbe lateral pterygoid and a surgical insertion of the superior lateral pterygoid muscle to the approach to treatment, Br Dent J 1982;1 S3;27. articular disc in rbe temporomandibular joint of human 23, Juniper RP, Temporomandihular joint dysfunction: A the- cadavers, Ausr Dent J 1989;34:3li-332, ory based upon electromyographic studies of the lateral Le Toux C, Duval JM, Darnault P, The human tempuro- pterygoid muscle. Br J Oral Maxillofac Surg 1984;22:1-S, mandibular joint: Current anatomic and physiologic sta- 24, Grant PC, Lateral pteryguid: Two muscles? Am J Anat tus, Surg Radiol Anat 1989;11:283-2S8, 1973;138:l-10, Carpentier P, Yung J-P, Margudles-Bonnet R, Meunissier 25, Carlsóo S, An electromyographic srudy of the activity and M, Insertions of tbe lateral pterygoid muscle: An anatomic an anatomical analysis of the mechanics of tbe lateral study of tbe buman remporomandibular joint, J Oral pterygoid muscle. Acra Anat 1956;26:339-351, Maxillofac Surg 1988;4Ê:477-^82, 26, McNamara AJ. The independent functions of the two Dauber W. Tbe adjacent srtucrural relationships of tbe beads of tbe lateral ptetygoid muscle. Am J Anat 1978; articular disk of the temporomandibular joint and its 138:197-206, functional importance, Scbweiz Monatsschr Zahnmed 27, Lipke DP, Gay T, Gross GD, Yaeger JA, An electtomyo- 1987;97:427-437, grapbic study of tbe buman lateral pterygoid muscle Sumnig W, Bartolain G, Fangbanel J, Histological studies [abstract 713], J Dent Res 1977;J6B:230, of the morpbological relationship of the lateral pterygoid 28, Burke RH, McNamara JA, Elettromyography after lateral muscle to the articular disk in the human rcmpuro- pterygoid myoromy in monkeys, J Oral Surg !979;37; mandibukr joint, Anat An; 1991; 173:279-286, 630-636, Warwick R, Williams PL, Gray^s Anatomy, ed 36, 29, Miller AJ, Vargervik K, Cbierici G. Electromyograpbic London: Cburcbill Livingstone, 1980, analysis of tbe functional components of the lateral ptery- Widmalm SE, Lillie JE, Asb MM. Anatomical and elcc- goid muscle in tbe rbesus monkey (Macaca mulatta). Arch rromyograpbic studies of tbe lateral pterygoid muscle, J Oral Biol 1932;27t475^80, Oral Rehabii 1987;14:429^46. 30, Gibbs CH, Maban PE, Wilkinson TM, Maudeili A, EMG Scmoike C, The relationship between the temporo- activity of tbe superior belly of the lateral pterygoid mus- mandibular joint capsule, articular disc and jaw muscles. J cle in relation to orher muscles, J Prostbet Dent 1984; Anat 1994;184:33,5-345, 59^691-702, Honée GLJM, The anatomy of the lateral pterygoid mus- 31, Wood W W, Takada K, Hannam AG, The elecrromyo- ds. Acra Morphol Neerl Scand 1972;IO:331-340, graphic activity of the inferior head of the human lateral Bancroft JD, Stevens A, Theory and Practice oí Hiscological pterygoid muscle during clenching and chewing. Arch Techniques, ed 2, London: Churcbill Livingstone, 1982. Oral Biol 198,i;31:245-253. Culling CFA. Handbook of Histopathological Techniques, 32, Johannson AS, Isberg A, Isaacson G, A radiograpbic and ed 3. London: Burterworrb, 1975, bisiologic study of tbe topographic relations in tbe tem- Flatau AT. Klineberg 1, An anatomical investigation of the poromandibular joint region: Implications for a nerve lateral pterygoid muicic, | Dent Res 1985;64:653, entrapment mecbanism, J Oral Maxillofac Surg 1990; Okeson JP, Management of Temporomandibular Disorders 48:953-961. and Occlusion. St Louis: Mosby Year Book, 1992.

Journal of Orofacial Pain 15 Heylings et ai

Resumen Zusammenfassung

Músculo pterigoideo iateral y el disco üemporomsn- M. pterygoideus lateralis und Kiefergelenksdrskus dibuiar Diese anatomische Studie prüfl die Insertion des ivl ptery- Este estudio anatómico examina ia inserción del niúscuio goideus laterals an der Kapsel und am Diskus dea pterigoideo iateral a la cápsula y disco de la articulación tem- Kieíergelenks. Die Anatomie des Kiefergelenks und seiner poromandibuiar (ATM). La anatomía de ia ATM y sus airede- Umgebung, insbesondere die insertion des Caput superior des dores, en particular ia inserción de la cabeza superior del mús- M. pterygoideus laterahs, wurde durch Sektion und konven- cuio pterigoideo laterai, fueron estudiadas por medio de tionelle histologische Techniken studiert Das Material bestand técnicas de disección y de histologie convencionai. Ei matenai aus 16 Präparaten von Personen, weiche 60 Jahre oder äiter consistió de 16 especímenes de cadáveres de individuos de > waren. Die Resultate zeigten, dass nur ein Teil des Caput supe- 60 años de edad Los resuitados indicaron que sóio una parte rior des M. pterygoideus lateralis mil dem vorderen Anteil der de la cabera superior dei músculo pterigoideo lateral eslá Kapsei verbunden ist, weiche ihrerseits fest mit dem Diskus adherida ai ia porción anterior de la oápsjia qje a su vez eslá verbunden ist, was den Eindruck einer direkten Verbindung des firmemente adherida ai disco, dando ia impresión de que ei Muskeis mit dem Diskus hervorruft Alle Präparate ieigten eine músculo y ei disco están conectados directamente. Todos los Verbindung des Caput superior des M. pterygoideuB lateralis especímenes mostraron una inserción de la cabeza superior dei mit dem anterioren mediaien Anteii der Kapsel, jedoch unter- músculo pterigoideo iateral a la porción media anterior de la cápsula, pero diversos grados de inserción al aspecto laíerai de schiedliche Grade der Befestigung am iateralen Anteil der ia cápsula de ia ATM La parte remanente de la cabeza superior Kiefergeienkskapsei. Der verbleibende Teii des Caput superior dei músculo pterigoideo iateral está adinerida ai cóndilo des M. pterygoideus iateraiis ist mit dem Condyius verbunden. mandibuiar. El seccionmiento consecutivo en ningún momento Senenschnitte zeigten in keinem Fall eine direkte Insertion vor demostró que existiera una inserción directa de las fibras de la Fasern des Caput supenor des M. pterygoideus lateralis in der cabeza superior dei músouio pterigoideo iaterai, dentro dei Diskus disco.

16 Volume 9, Number 1, 1995