muscles of mastication

Muscles of Mastication

ByGaurav KetkarNirmitee GujarathiSharvari VichareManasi Kenjale

Movements

Depression of mandible

Elevation of manible

Protraction of mandible

Retraction of mandible

Side to side movement

The chief muscles of mastication

• Masseter muscle• Temporalis muscle• Medial pterygoid muscle• Lateral pterygoid muscle

Masseter muscle

• Thick, somewhat quadrilateral muscle

• It has two heads: superficial and deep

Deep part

Superficial part

The superficial portion of Masseter

•The largest of the two heads

•Origin: It arises by a thick, tendinous aponeurosis from the zygomatic process of the maxilla, and from the anterior two-thirds of the lower border of the zygomatic arch.

•Insertion: Its fibers pass downward and backward, to be inserted into the angle and lower half of the lateral surface of the ramus of the mandible.

The deep portion of Masseter muscle

• Much smaller, but more muscular in texture

• Origin: it arises from the posterior third of the lower border and from the whole of the medial surface of the zygomatic arch.

Insertion: its fibers pass downward and forward, to be inserted into the upper half of the ramus

• Action:

elevates and protrudes the mandible thus closing the mouth;

deep fibers retrudes it.

• Innervation:

Mandibular division of trigeminal nerve through masseteric nerve which passes through ? To enter its deep surface.

• Blood supply:

masseteric artery from maxillary artery

Temporalis muscle • is a broad, radiating muscle,

situated at the side of the head.

• Origin: It arises from the whole of the temporal fossa and the deep surface of temporal fascia

• Insertion: Its fibers converge as they descend, and end in a tendon, which passes deep to the zygomatic arch and is inserted into the medial surface, apex, and anterior border of the coronoid process, and the ant. Border of mandibular ramus

• Action:

its anterior and middle fibers elevate the mandible thus closing the mouth; its posterior fibers retrudes it.

• Innervation: Deep temporal branches of mandibular

nerve.

Lateral pterygoid muscle

• Has two heads: superior and inferior

• Origin: the superior head arises from greater wing of sphenoid bone while the inferior head arises from the lateral surface of the lateral pterygoid plate

• Insertion: fibers pass backward to be inserted into the neck of mandible and articular disc of TMJ.

• Innervation:

Ant. division of mandibular nerve through lateral pterygoid nerve

Blood supply: maxillary artery through the pterygoid branch.

• Action:

acting together they protrude and depress the mandible;

acting alone and alternatively they produce side to side movements of the mandible.

(rotates the mandible to

the opposite side)

Medial pterygoid muscle

• It has two heads: superficial and deep

• Origin: the superficial head arises from the maxillary tuberosity. The deep head arises from medial surface of the lateral pterygoid plate

• • Insertion: fibers run downward,

backward and laterally and are inserted into the medial surface of the angle of the mandible

• Innervation:

main trunk of mandibular nerve through nerve to medial pterygoid

Blood supply:

Maxillary artery through the medial pterygoid artery

• Action:

assets in elevating and protrusion of the mandible

acts together with lat. Pterygoid of the same side in rotating the mandible

Side to side movement

It is done by alternate contraction and relaxation of medial and lateral pterygoids of opposite side.

Applied Aspect

Any dammage to branch of mandibular never supplying muscles of mastication may lead to paralysis of these muscles.