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Jesse Wilson 17394150 Muscles of Mastication LO6 6. For each of the following muscles state its innervation and apply principles M4-M7 to describe its attachments and actions: Muscle Muscles of Mastication Temporalis Origin Insertion Innervation Position & Orientation Function Temporal fossa Coronoid process of mandible Mandibular division of trigeminal nerve (CN V3) Triangular muscle with vertical fibers at the front and horizontal fibers at the back. All fibres: elevation of mandible at Jesse Wilson 17394150 TMJ Temporal fascia Anterior border of ramus of mandible Posterior: retraction of the mandible at TMJ Often separated into anterior, middle and posterior fibers Masseter Medial surface and inferior border of zygomatic bone Lateral surface and ramus and angle of mandible Mandibular division of trigeminal nerve (CN V3) Quadrate muscle Elevates mandible at TMJ joint Oblique fibers that are almost vertical! Makes a limited contribution to protrusion at TMJ along with lateral pyerygoid Medial surface of Medial surface of lateral pterygoid ramus and angle plate of mandible Mandibular division of trigeminal nerve (CN V3) Mirror image of ipsilateral Bilateral: elevation and protraction masseter. of mandible at TMJ Zygomatic arch Medial pterygoid Lateral pterygoid Lateral surface of Superior head: lateral pterygoid TMJ articular disc plate TMJ joint capsule Mandibular division of trigeminal nerve (CN V3) Oblique fibers that are almost vertical! Unilateral: smaller grinding movements Transverse fibers Bilateral: Protraction and depression of mandible at TMJ Inferior head: Neck of mandible Masseter and temporalis muscles both have long leaver arms which increases the mechanical advantage of these muscles. Enables them to produce force up to 80N!! Unilateral: lateral displacement (swings jaw towards contralateral side) at TMJ Jesse Wilson 17394150 Suprahyoid Muscles Digastric Base of cranium Mastoid process Facial and mandibular nerves Anterior and posterior muscle bellies Depresses mandible against resistance when infrahyoid muscles fix hyoid bone Fixed to hyoid by sling Geniohyoid Mylohyoid Anterior body of the posterior surface of the mandible Medial body of the posterior surface of the mandible Hyoid bone Nerve to geniohyoid Hyoid bone Mandibular nerve Depresses mandible against resistance when infrahyoid muscles fix hyoid bone Forms the floor of the oral cavity Depresses mandible against resistance when infrahyoid muscles fix hyoid bone Accessory muscles of mastication because can only act on the mandible in combination with the infrahyoid muscle which stabilize the hyoid bone. Jesse Wilson 17394150 Jesse Wilson 17394150 Jesse Wilson 17394150 Actions of Primary Muscles of Mastication