Masticatory Muscles
The masticatory muscles proper comprise the masseter, temporalis, medial, and lateral pterygoid muscles. Adjunct masticatory muscles include the suprahyoid muscles provided the hyoid bone is fixed in a stable position relative to the mandible. Masticatory
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The masticatory muscles can be considered the engines of mandibular jaw movements. The main masticatory muscles include the masseter, temporalis, medial, and lateral pterygoid muscles (Table 26.1) (Figs. 26.1 and 26.2). They all originate from the cranium (fixed part) and extend to various parts of the mandible (mobile part). Tendon attachments of the masticatory muscles show periosteal, osseous, or cartilaginous insertions (Hems and Tillmann 2000). The masticatory muscles are all innervated by branches from the
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mandibular nerve extending as the third division of the trigeminal nerve (CN V). The highly complex pattern of mandibular jaw movements depend on which muscles are active and whether they contract uni- or bilaterally. The suprahyoid musculature may also contribute to mandibular jaw movements, provided the hyoid bone is fixed in a stable position relative to the mandible (Chap. 24). However, the suprahyoid muscles are only considered as an adjunct to the main masticatory muscles.
Table 26.1 The main masticatory muscles Muscle Masseter
Origin Zygomatic arch
Temporalis
Temporal lines of parietal bone
Medial pterygoid
Pterygoid process, tuberosity
Lateral pterygoid
Pterygoid process, pyramidal process of palatine bone, tuberosity
Insertion Lateral aspect of ramus
Innervation Masseteric branch (from mandibular nerve CN V3) Coronoid process, Deep temporal anterosuperior border branches (from of ramus mandibular nerve CN V3) Medial aspect of Medial pterygoid ramus branches and occasional branches from lingual nerve (all from mandibular nerve CN V3) Condyle, Lateral pterygoid anteromedial part of branch, deep disk temporal branches, masseteric branch, buccal nerve (all from mandibular nerve CN V3)
Major function Synergistic relative to mandible muscles Elevation Temporalis, medial pterygoid
Elevation, retrusion Masseter, medial pterygoid
Elevation, protrusion, laterotrusion
Masseter, temporalis, lateral pterygoid
Protrusion, laterotrusion
Medial pterygoid
Antagonistic muscles Suprahyoid musculature (hyoid bone must be fixed) Suprahyoid musculature (hyoid bone must be fixed) Suprahyoid musculature (hyoid bone must be fixed)
Temporalis
For details see text
© Springer International Publishing Switzerland 2017 T. von Arx, S. Lozanoff, Clinical Oral Anatomy, DOI 10.1007/978-3-319-41993-0_26
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26 Masticatory Muscles
TM
LPMsh LPMih
MM
Fig. 26.1 Illustration of right masseter and temporalis muscles. MM masseter muscle, TM temporalis muscle
MPM
Fig. 26.2 Illustration of right medial and lateral pterygoid muscles. LPMih inferior head of lateral pterygoid muscle, LPMsh superior head of lateral pterygoid muscle, MPM medial pterygoid muscle
Masseter Muscle
Masseter Muscle The masseter muscle is covered by the masseteric fascia and is formed by three muscular layers. This muscle extends from the zygomatic bone and the zygomatic arch to the ramus of the mandible (Figs. 26.3, 26.4, 26.5, 26.6, 26.7, 26.8, and 26.9). The masseter has a typical penniform structure and is divided into three
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