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Lateral Pterygoid Muscle (lateral + pterygoid_muscle)

Distribution by Scientific Domains

Medical Sciences	80%

Selected Abstracts

Activity of superior head of human lateral pterygoid increases with increases in contralateral and protrusive jaw displacement

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2007
Manish K. Bhutada
The hypothesis was that the superior head of human lateral pterygoid muscle (SHLP) plays a similar role in jaw movement as the inferior head of human lateral pterygoid muscle (IHLP). The aims were to determine the functional properties of SHLP single motor units (SMUs) and root mean square activity (RMS) of the SHLP during contralateral and protrusive jaw movement tasks and to compare these features with those identified previously for the IHLP. In 22 human subjects, SMUs were recorded intramuscularly from computer tomography-verified sites within the SHLP during standardized contralateral and protrusive jaw movement tasks recorded by a jaw-tracking device. Of the 50 SMUs discriminated, 39 were active during contralateral and 29 during protrusive jaw movements. The firing rates and RMS of the SHLP motor units increased with an increase in jaw displacement. The RMS activity across the entire trial during contralateral jaw movement was significantly greater than that during protrusion. Similarly to conclusions previously identified for the IHLP, the data are consistent with an important role for the SHLP in the control of contralateral and protrusive jaw movements. The similarities in SHLP and IHLP functional properties support the proposal that both heads should be regarded as a system of fibers acting as one muscle. [source]

Is the superior belly of the lateral pterygoid primarily a stabilizer?

JOURNAL OF ORAL REHABILITATION, Issue 6 2001
An EMG study
The aim of the present study was to compare the activity levels within the two bellies of the lateral pterygoid muscle between different jaw positions to test the hypothesis that the upper head is primarily a stabilizer. Electromyographic (EMG) recordings, using monopolar concentric needle electrodes, were made from 14 healthy subjects during mandibular rest position (RP), clenching in intercuspal position and jaw opening, first about 10 mm and then about 25 mm. Both bellies had very little activity during RP. The activity level of the superior belly was high during clenching and large opening (LO) with a dip during low opening degree. This pattern differed from that of the inferior belly where the activity was relatively low during clenching and then gradually increased to its highest level during LO. The results support that the lower belly is primarily a jaw opener while the superior belly acts as a stabilizer keeping the disc and condyle in a functionally stable position during clenching and jaw movements. [source]

Discal attachments of the human temporomandibular joint

AUSTRALIAN DENTAL JOURNAL, Issue 3 2005
JE Christo
Abstract Background: Despite its clinical significance, the anatomy of the human temporomandibular joint (TMJ) and its relationship to the lateral pterygoid muscle remains poorly described and often misrepresented in standard texts. The aim of this study was to describe how the anterior and posterior attachments of the TMJ disc vary between lateral, central and medial regions of the joint. Methods: Ten left TMJs were removed en bloc from cadavers and serial sections were made at 3,4mm intervals. Observations were made to ascertain the anterior and posterior attachments of the disc and the joint structures were traced from standardized photographs. Results: Laterally, the capsule and lateral discal ligament merged prior to their attachment at the condylar pole. Medially, muscle fibres, capsule and the disc converged on the medial pole of the condyle. There was no evidence that fibres of the upper head of the lateral pterygoid muscle inserted directly into the disc. The upper head inserted into the condyle either directly at the pterygoid fovea or via a central tendon or indirectly via the capsule. Posteriorly, the superior part of the posterior attachment of the disc attached to the cartilaginous meatus and tympanic part of the temporal bone. The inferior part of the posterior attachment of the disc attached to the posterior surface of the condyle. In four joints, this attachment was folded beneath the posterior band of the disc, creating a wedge-shaped flap that ran medio-laterally. Conclusion: This study is in broad agreement with other anatomical TMJ studies but there are two main points of difference. Firstly, a true muscle insertion of the superior head of the lateral pterygoid muscle to the disc was not observed. Secondly, a wedge-shaped flap of retrodiscal tissue was identified between the condyle and the disc. [source]

Penetration of muscles by branches of the mandibular nerve: A possible cause of neuropathy

CLINICAL ANATOMY, Issue 1 2004
Takashi Shimokawa
Abstract We carried out detailed dissections of the branches of the mandibular nerve and muscles innervated by these branches to investigate their positional relationships. We made the following observations: 1) small branch of the auriculotemporal nerve penetrated the lateral pterygoid muscle; 2) the entire lingual nerve penetrated the medial pterygoid muscle; and 3) branch of the mylohyoid nerve penetrated the mylohyoid muscle and communicated with the submandibular ganglion. No detailed descriptions of these nerve branches have been reported previously. The existence of these nerve branches that penetrate muscles might result in the neuralgic pain in the trigeminal region when such pain is of unknown origin. Clin. Anat. 17:2,5, 2004. © 2003 Wiley-Liss, Inc. [source]

Time series analysis of jaw muscle contraction and tissue deformation during mastication in miniature pigs

JOURNAL OF ORAL REHABILITATION, Issue 1 2004
Z. J. Liu
summary, Masticatory muscle contraction causes both jaw movement and tissue deformation during function. Natural chewing data from 25 adult miniature pigs were studied by means of time series analysis. The data set included simultaneous recordings of electromyography (EMG) from bilateral masseter (MA), zygomaticomandibularis (ZM) and lateral pterygoid muscles, bone surface strains from the left squamosal bone (SQ), condylar neck (CD) and mandibular corpus (MD), and linear deformation of the capsule of the jaw joint measured bilaterally using differential variable reluctance transducers. Pairwise comparisons were examined by calculating the cross-correlation functions. Jaw-adductor muscle activity of MA and ZM was found to be highly cross-correlated with CD and SQ strains and weakly with MD strain. No muscle's activity was strongly linked to capsular deformation of the jaw joint, nor were bone strains and capsular deformation tightly linked. Homologous muscle pairs showed the greatest synchronization of signals, but the signals themselves were not significantly more correlated than those of non-homologous muscle pairs. These results suggested that bone strains and capsular deformation are driven by different mechanical regimes. Muscle contraction and ensuing reaction forces are probably responsible for bone strains, whereas capsular deformation is more likely a product of movement. [source]