MUSCLES OF MASTICATION

Group 3

MUSCLES OF MASTICATION

The muscles which are required for mastication are known as the muscles of mastication

These muscles help mainly in the movement of the mandible and not the maxilla as maxilla is an integral part of the skull and the mandible being the only movable bone in the skull.

PRIMARY MUSCLES OF MASTICATION

MASSETER MUSCLE

It is one of the main muscle which helps in the process of mastication

-In humans, the masseter is the second most efficient masticatory muscle.

-Its origin and insertion make it very useful for the movement of the jaw and for applying good bite force for mastication.

-Masseter muscle is a powerful muscle because of its Multipennate arrangement of fibers

MASSETER MUSCLE

-The masseter muscle extends from the zygomatic arch to the ramus and body of the mandible.

-The fibers of this muscle are broad, extending from the region of the second molar on the surface of the mandible to the surface of the ramus.The muscle is divided into 2 parts

Superficial Deep

MASSETER MUSCLE

Origin: Superficial layer – anterior 2/3rd of

lower border of zygomatic arch & zygomatic processof maxilla

Middle layer – anterior 2/3rd of deep surface & posterior 1/3rd of lower border of zygomatic arch

Deep layer – deep surface of zygomatic arch

MASSETER MUSCLE

Insertion :  Superficial layer –lower part of

lateral surface of ramus of mandible  Middle layer –middle part of ramus  Deep layer – upper part of the

ramus & coronoid process

MASSETER MUSCLE

The main function of masseter muscle is

Elevation of the mandible lateral movements of the

mandible for efficient chewing and grinding of the food

unilateral chewing Retraction of the mandible

MASSETER MUSCLE

TEMPORALIS MUSCLE

-This is the muscle which helps in elevation of the mandible, It is one of the muscles of mastication.

-It is large shaped in appearance and covers the Temporal area of the skull.

Origin and Insertion: From the Parietal bone of the skull and

is inserted on the coronoid process of the mandible.

TEMPORALIS MUSCLE

Functions: Elevation of the mandible Retraction of the mandible. Crushing of food between the molars. Posterior fibers draw the

mandible backwards after it has been protruded.

It is also a contributor to side to side grinding movement.

TEMPORALIS MUSCLE

LATERAL PTERYGOID MUSCLE

-This is a small muscle which also helps in the mastication process.

-It is divided into 2 heads Origin: Upper head – infratemporal surface

& crest of greater wing of sphenoid bone

Lower head – lateral pterygoid plate

LATERAL PTERYGOID MUSCLE

Insertion : Pterygoid fovea on the anterior surface

of neck of mandible Anterior margin of articular disc &

capsule of TMJ Functions: Depresses the mandible Protrudes it forward for opening of the

jaw Side Movements

LATERAL PTERYGOID MUSCLE

MEDIAL PTERYGOID MUSCLE

-It is a thick muscle of mastication. Origin and Insertion : It Arises from the deep head the

lateral pterygoid plate, and from the maxillary tuberosity.

Insertion is seen on the Medial angle of the Mandible.

MEDIAL PTERYGOID MUSCLE

Functions: Elevates the mandible, Closes the jaw, Helps in side to side movement.

MEDIAL PTERYGOID MUSCLE

ACCESSORY MUSCLES OF MASTICATION

Group 3

SUPRAHYOID MUSCLES

It is the region above or superior to the hyoid bone in the neck.

It includes the digastric, stylohyoid, mylohyoid, and the geniohyoid muscles.

SUPRAHYOID MUSCLES

The digastric muscle double muscle of the throat which is located

under the chin, behind and below the corner of the jaw, immediately in front of the top of the sternocleidomastoid, one for each side of the jaw and neck.

The digastric is made up of an anterior and posterior belly.

The anterior belly extends from the digastric fossa of the mandible

The posterior belly extends from the mastoid notch of the temporal bone.

Digastric muscle

SUPRAHYOID MUSCLES

The stylohyoid muscle muscle located in the neck thin and slender and is attached to the hyoid

bone The muscle lifts the hyoid bone during

swallowing, which gives the characteristic in and out appearance of swallowing

It lifts the base of the tongue up when swallowing.

It is located just in front of the digastric muscle. Which lifts the tongue back when swallowing.

Stylohyoid muscle

SUPRAHYOID MUSCLES

The mylohyoid muscle triangular muscle on each side of the mouth

that is located above the anterior belly of the digastric muscle

extends from the inner surface of the mandible to the hyoid bone

forms the floor of the mouth depresses the mandible and elevates the hyoid It is important in swallowing

Mylohyoid muscle

SUPRAHYOID MUSCLES

The geniohyoid muscle  it is a narrow muscle situated superior

to the medial border of the mylohyoid muscle.

acts to raise the hyoid bone and draw it forward and to retract and depress the lower jaw

Geniohyoid muscle

INFRAHYOID MUSCLES

These muscles are often referred to as strap muscles due to their ribbon-like appearance.

They are located inferior to the hyoid bone.

These muscles anchor the hyoid bone and depress the hyoid and larynx during swallowing and speaking.

It includes the sternohyoid, thyrohyoid, and the omohyoid muscles.

INFRAHYOID MUSCLES

The Sternohyoid Muscle This is a thin, narrow, strap muscle that is

superficial except inferiorly where it is covered by the sternocleidomastoid muscle.

Inferior attachment: manubrium of sternum and medial end of clavicle.

Superior attachment: body of hyoid bone. Innervation: C1, C2, C3 from ansa cervicalis. It depresses the hyoid bone after it has been

elevated during swallowing. It also helps to steady the hyoid during

movements of the tongue, larynx and pharynx.

Sternohyoid Muscle

INFRAHYOID MUSCLES

The Thyrohyoid Muscle This muscle appears to be the superior

continuation of the sternothyroid muscle. Inferior attachment: oblique line of thyroid

cartilage. Superior attachment: inferior body of body and

greater horn of hyoid bone. Innervation: C1 via hypoglossal nerve (CN XII). It depresses the hyoid bone and elevates the

larynx. It is mainly responsible for preventing food from

entering the larynx during swallowing (it pulls the larynx and hyoid bone together)

Thyrohyoid Muscle

INFRAHYOID MUSCLES

The Omohyoid Muscle This muscle has two bellies that are united by an

intermediate tendon, which is connected to the clavicle by a fascial sling.

The omohyoid muscle is an important landmark in the neck because it divides the anterior and posterior triangles into smaller triangles.

Inferior attachment: superior border of scapula near the suprascapular notch.

Superior attachment: inferior border of hyoid bone. Innervation: C1, C2, C3 by a branch of ansa

cervicalis. It depresses, retracts and steadies the hyoid during

swallowing and speaking.

Omohyoid Muscle