muscles of mastication
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MUSCLES OF MASTICATION
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Muscles of Mastication :
1. MASSETER Muscles2. TEMPORALIS Muscles3. LATERAL PTERYGOID Muscle4. MEDIAL PTERYGOID Muscle
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The Muscles of Mastication have common characteristics :
• All are inserted to the mandible• All are innervated by the mandibular division of the Trigeminal Nerve • All are concerned in biting and chewing
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I. Masseter muscle
• Is a flat , quadrangular muscles, partly tendinous, partly fleshy.
Origin: The superficial portion originates from the anterior 2/3 of the lower border of the zygomatic arch while the deeper portion originates from the whole length of deep surface of the zygomatic arch.
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Insertion : is the lateral surface of coronoid process, ramus and gonion
Action : Is to elevate the jaw, with superficial fibers causing protraction
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II. Temporalis muscles
• Is a large , fan-shaped muscle on the side of the head
Origin: is the floor of the temporal fossa and the temporal fascia. Course: the anterior fibers run vertically downwards while the posterior fibers are almost horizontal in position.
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Insertion : Is the apex and deep surface of the coronoid process and along the anterior border of the ramus down to the last lower molar tooth.
Action : the anterior fibers will elevate the mandible, while the posterior fibers will retract the mandible
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III. Lateral Pterygoid muscle :
• Is a thick triangular muscle muscle with two heads.
Origin : the superior portion is the infratemporal surface of the great wing of the sphenoid. While, the inferior portion originates from the lateral surface of the lateral pterygoid plate.
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Insertion : the fibers are directed laterally and backwards into the front of the neck of the mandible and into the capsule of TMJ.
Action : is to depress , protrude and move the mandible from side to side
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IV.Medial Pterygoid muscle
• Is quadrilateral in shape
Origin : is from the medial surface of the
lateral pterygoid plate , the
posterior surface of the tubercle of
palatine bone and tuberosity of the
maxilla.
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Insertion: is into the triangular impression on the medial surface of the mandible between its mylohyoid groove and angle.
Action : is to elevate and to protract the mandible. It also moves the jaw from side to side when acting singly.
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