Muscles Of Mastication

Question 1

Muscles of mastication

Answer 1

Temporalis
Masseter
Lateral pterygoid
Medial pterygoid

All innervated by the trigeminal nerve (CN V3) from the first branchial arch

Question 2

Temporalis

Answer 2

Origin: From the temporal fossa

Insertion: tip and medial surface of the Coronoid process extending into the retromolar fossa posterior to the most distal mandibular molar

Function: elevation and retraction of the mandible

Temporalis muscle is covered by the temporal fascia also know as the temporal aponeurosis

Question 3

Masseter

Answer 3

Consists of two head: Superfial and Deep

Superficial head: originates from the aponeurosis of the maxillary process of the zygomatic arch and inferior border of the zygomatic arch (anterior 2/3)

Insertion: lateral surface of angle and ramus of mandible

It’s fibers pass down and backward and insert into the angle of the mandible

Deeper head: smaller, originates from the lower border and medial surface of the zygomatic arch (posterior 3rd)
It’s fibers pass down and forward to be inserted into the upper half of the ramus and lateral surface of the coronoid process of the mandible

Function: elevates and protrudes mandible to close jaw

Question 4

Medial pterygoid

Answer 4

Has two heads superficial and deep

Deep head: originates from the medial surface of the lateral pterygoid plate

Superficial head: smaller and originates from the maxillary tuberosity and the pyramidal process of the palatine bone

It’s fibers pass downward, lateral, and posterior into the lower back part of the medial surface of the ramus and angle of the mandible as high as the mandibular foramen

The insertion joins the masseter muscle to form a common tendinitis sling which allows the medial pterygoid and Masseter to be powerful elevators of the jaw

Question 5

Medial pterygoid muscle

Answer 5

Origin: superficial head- tuberosity of maxilla
Deep head- medial surface of lateral pterygoid plate and palatine bone

Insertion: medial surface of ramus and angle of mandible

Function: Together they elevate and protract (or protrude) mandible. Individually, they move mandible side to side

Question 6

Lateral pterygoid

Answer 6

Superior and inferior head

Superior head: originates on the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone and inserts onto the articulate disc and fibrous capsule of the TMJ

Inferior head- originates from the lateral surface of the lateral pterygoid plate and inserts onto the neck of condyloid process of the mandible

Function: pull the head of the condyle out of the mandibular fossa along the articular eminence to protrude the mandible

Lateral pterygoid is the only muscle of mastication that assists in depressing the mandible (opening the jaw)

It’s assisted in digastric, mylohyoid and geniohyoid

Question 7

Trismus “lockjaw”

Answer 7

Common causes:

Damage to the joints (muscle or nerves located in and around the jaw area)

Incorrect local anesthesia technique is mboli ngaa the medial pterygoid muscle

Inflammation of the muscles