MUSCLES OF MASTICATION

Muscles of Mastication :

1. MASSETER Muscles2. TEMPORALIS Muscles3. LATERAL PTERYGOID Muscle4. MEDIAL PTERYGOID Muscle

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

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.

Insertion : is the lateral surface of coronoid process, ramus and gonion

Action : Is to elevate the jaw, with superficial fibers causing protraction

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.

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

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.

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

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.

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.

THE END