TMJ and Muscles of Mastication

Question 1

What are the main parts of the mandible?

Answer 1

Body
Ramus
Angle
Coronoid process
Condylar process - head and neck

Question 2

What is the mandibular symphysis?

Answer 2

Mandible is in 2 parts during development
This is where the parts are fused

Question 3

Where is the mental foramen found?

Answer 3

Inferior to the first and second premolars

Question 4

What is the mandibular fossa and where is it found?

Answer 4

Where the mandible articulates with the skull
Found in the temporal bone, anterior to the external acoustic meatus and near the zygomatic arch

Question 5

Where does the TMJ articulate?

Answer 5

Mandibular fossa of the temporal bone and the condylar process of the mandible

Question 6

What type of joint is the TMJ?

Answer 6

Modified hinge (atypical) synovial joint

Question 7

What type of cartilage is found in the TMJ?

Answer 7

Fibrocartilage

Question 8

Describe the cavities of the TMJ?

Answer 8

Fibrocartilaginous articular disc separates the joint into superior and inferior articular cavities

Question 9

What are the ligaments of the TMJ?

Answer 9

2 extrinsic:
Sphenomandibular ligament
Stylomandibular ligament
1 intrinsic:
Lateral ligament

Question 10

What do the TMJ ligaments do?

Answer 10

Connect the mandible to the cranium

Question 11

What is the function of the sphenomandibular ligament and where does it run?

Answer 11

Provides primary passive support of the mandible and acts as a fulcrum for the TMJ
Runs from spine of the sphenoid bone to the lingula of the mandible

Question 12

What is the function of the stylomandibular ligament and where does it run?

Answer 12

It’s technically a thickening of the capsule of the parotid gland - doesn’t contribute to strength
Runs from styloid process to angle of the mandible

Question 13

What is the function of the lateral ligament and how is it formed?

Answer 13

Strengthens TMJ laterally and acts to prevent posterior dislocation of the joint together with the postglenoid tubercle
Formed by thickened part of the joint capsule

Question 14

What are the 5 mandibular movements at the TMJ?

Answer 14

Protrusion
Retraction
Elevation
Depression
Lateral movements

Question 15

Describe protrusion of the TMJ and name the muscles its actioned by

Answer 15

Gliding movements between temporal bone and articular disc in the superior cavity
Actioned by lateral pterygoid, masseter and medial pterygoid

Question 16

Describe retraction of the TMJ and name the muscles its actioned by

Answer 16

Gliding movements between the temporal bone and articular disc in the superior cavity
Actioned by posterior fibres of temporalis, masseter and geniohyoid and digastric

Question 17

Describe elevation of the TMJ and name the muscles its actioned by

Answer 17

Hinge and rotational movements between head of mandible and articular disc in the inferior cavity
Actioned by the temporalis, masseter and medial pterygoid

Question 18

Describe depression of the TMJ and name the muscles its actioned by

Answer 18

Hinge and rotational movements between head of mandible and articular disc in the inferior cavity
Actioned by gravity, digastric, geniohyoid and mylohyoid

Question 19

Describe lateral movement of the TMJ and name the muscles its actioned by

Answer 19

Grinding and chewing
Actioned by the temporalis on the same side and the pterygoids on the opposite side with support from the masseter

Question 20

When is the TMJ most unstable and why is this?

Answer 20

During depression as the condylar processes move anteriorly and lie underneath the articular eminences with the mandibular head being vulnerable to anterior dislocation into the infratemporal fossa

Question 21

Describe anterior dislocation of the TMJ

Answer 21

Heads of the mandible may be dislocated anteriorly so they pass anterior to the articular tubercles through excessive contraction of the lateral pterygoids

Question 22

Describe posterior dislocation of the TMJ

Answer 22

Uncommon as it is resisted by the postglenoid tubercle and the strong intrinsic lateral ligament

Question 23

Describe arthritis of the TMJ

Answer 23

TMJ becomes inflamed and resultant abnormal function of the TMJ may cause structural problems such as dental occlusion and joint clicking (crepitus)

Question 24

Which pharyngeal arch are the muscles of mastication derived from?

Answer 24

1st pharyngeal arch

Question 25

Where does the temporalis originate and insert?

Answer 25

Originates from temporal fossa and fascia
Inserts at coronoid process of mandible and anterior border of ramus near last molar

Question 26

What is the function of the temporalis?

Answer 26

Retracts and elevates the mandible
Assists in closing the mouth

Question 27

Where does the masseter originate and insert?

Answer 27

Originates from maxillary process of zygomatic bone and anterior 2/3 of inferior border of zygomatic arch
Inserts at the angle and lateral surface of ramus

Question 28

What is the function of the masseter?

Answer 28

Elevates the mandible

Question 29

Where’s does the lateral pterygoid originate and insert?

Answer 29

Originates from infratemporal surface of greater wing of sphenoid bone and lateral surface of lateral pterygoid plate
Inserts on the front of the neck of the mandible

Question 30

What is the function of the lateral pterygoid?

Answer 30

Protrudes the mandible
Assists medial pterygoid with lateral movements
Depresses the mandible

Question 31

Where does the medial pterygoid originate and insert?

Answer 31

Originates from medial surface of lateral pterygoid plate and maxillary tuberosity and pyramidal process of palatine bone
Inserts into medial surface of the ramus and angle of mandible

Question 32

What is the function of the medial pterygoid?

Answer 32

Elevates the mandible and assists with lateral movements