Joints: TMJ & Muscles of Mastication

Question 1

What’s this? What does it connect?

Answer 1

stylomandibular ligament

connects styloid process and mandibular angle

Question 2

What is this?

What does it connect?

Answer 2

Sphenomandibular Ligament

connects spine of sphenoid to lingula of mandible (inner/medial surface of mandibular ramus)

Question 3

What is this? What does it connect?

Answer 3

Temporomandibular Ligament

• zygomatic arch to condylar process of mandible

Question 4

What are the movements of the TMJ?

Answer 4

1. raising and lowering jaw
2. protrusion and retraction
3. side-to-side movement (grinding)
4. combined movements = chewing

Question 5

What is the axis of the TMJ?

Why is the location of its axis significant?

Answer 5

• a transverse axis through the mandibular lingula
• the lingula is a site of entry for a nerve into the mandible and since no movement happens at the axis, this is a safe place for it

Question 6

What kind of joint is the TMJ?

2 terms…

Answer 6

Condyloid Synovial Joint

and/or

Ginglymoarthrodial Joint

(ginglymus = hinge

arthrodial = sliding)

Question 7

The jaw opens via two movements of the TMJ.

What are they?

How much opening does each movement result in?

Answer 7

Hinge-like rotation - opens the first 20 mm or so

Forward/downward translation/gliding - the next 20-30 mm

Question 8

What lines the head of the mandible and the mandibular fossa?

Answer 8

fibrocartilage

Question 9

What is the articular disc of the TMJ made of?

Answer 9

fibrocartilage

Question 10

What are the two separate joints of the TMJ called?

Answer 10

discotemporal - btwn disc and mandibular fossa, responsible for translational gliding

discomandibular - btwn disc and head of mandible, responsible for hinge-like rotation

Question 11

What are the muscles of mastication?

Answer 11

1. masseter
2. temporalis
3. medial pterygoid
4. lateral pterygoid

Question 12

Answer 12

Lateral Pterygoid

COURSE:

• runs from greater wing of sphenoid + pterygoid plate to condyloid process of mandible

ACTIONS:

• opens mouth/depresses mandible
• protrudes and moves mandible side-to-side

Question 13

Answer 13

Medial Pterygoid

COURSE:

• lateral pterygoid plate, pyramidal process of palatine + maxillary tuberosity > medial mandibular angle

ACTION:

• elevates mandible
• helps lateral pterygoid with grinding

Question 14

Answer 14

Masseter

COURSE:

• zygomatic arch (deep) + maxilla (superficial) > coronoid process/ramus of mandible

ACTION:

• closes/elevates mandible
• protracts jaw

Question 15

Answer 15

Temporalis

COURSE:

• temporal lines > coronoid process of mandible

ACTION:

• elevates mandible
• retracts mandible

Question 16

What innervates all the muscles of mastication?

Answer 16

3rd division of the trigeminal nerve (CN V) known as the mandibular nerve

Question 17

Name the numbers.

4 and 6 are the two separate joints

Answer 17

1. Temporal Bone (Petrous Part)
2. Mandibular Fossa
3. Articular Disc (fibrocartilage)
4. Discotemporal Joint
5. Articular Capsule
6. Discomandibular Joint
7. Head of Mandible
8. Articular Tubercle