The TMJ and Infratemporal Fossa

Question 1

What 2 bones make up the skull?

Answer 1

Cranium + Mandible

Question 2

In an adult what is the only movable joint?

Answer 2

Temporomandibular Joint

Question 3

What joins the R and L parts of the mandible?

Answer 3

Midline fibrous joint – mental symphisis

Question 4

Which part of the mandible is the portion that

a) articulates with skull
b) non-articulating portion
c) located at the internal ridge
d) where nerves exit into chin to supply the skin of the face

Answer 4

a) Condylar Process → articulates with skull
b) Coronoid Process → non-articulating portion
c) Alveolar Process → internal ridge
d) Mental foramen

Question 5

Label the following parts of the mandible:

1. Condylar Process
2. Coronoid Process
3. Ramus
4. Angle
5. Body
6. Mental foramen
7. Alveolar arch

Answer 5

Question 6

What 2 foramina are found in the mandible and state which is medial (inner) and which is lateral (outer)

What important nerve(s) passes through these?

Answer 6

Mandibular foramen: medial (inside)

Mental foramen: lateral (outside)

The inferior alveolar nerve (branch of V3) passes IN through the mandibular foramen to supply the teeth and jaw, and then exits out via the mental foramen as the mental nerve

Question 7

Which part of the mandible holds the teeth?

Answer 7

The alveolar process (whole structure = alevolar arch)

Question 8

What type of joint is the TMJ and therfore what MUST it have?

Describe this and incl what it allows

Answer 8

Synovial joint

Therfore the TMJ has a fibrous capsule which is relatively thin and loose to allow movement, but sacrifices stability

Question 9

List 2 functions of the TMJ

Answer 9

1) allows articulation between cranium and mandible
2) facilitates jaw movement

Question 10

List the 3 bony points that articulate in the TMJ and label them on the image below

Answer 10

1) mandibular fossa
2) articular tubercle
3) head of the mandible

1 and 2 are on the base of the skull and 3 is the condylar process

Question 11

What is the main function of the Articular tubercle?

Answer 11

Prevents jaw from dislocating anteriorly

(it also forms part of the opening of the jaw)

Question 12

What covers the 2 articulating surfaces of the TMJ?

Answer 12

fibrocartilage

Question 13

What divides the TMJ into 2 synovial cavities?

Describe the location of each cavity

Answer 13

A fibrocartilage disc separates the joint into a superior and inferior cavity

Superior cavity: between the temporal bone and the upper disc surface

Inferior cavity: between the mandibular condyle and the inferior disc surface

Question 14

What does having 2 synovial cavities allow for in the TMJ?

Answer 14

allows a wide variety of movement to occur within the joint

Question 15

Why is articular disc necessary within the TMJ?

Answer 15

Because the bones are poorly aligned so the disc’s shape allows them to fit

Highly mobile joint means the disc provides some stability

Question 16

Describe the shape of the articular disc in terms of:

1) its upper surface
2) lower surface
3) thickness across the disc

Answer 16

1) upper surface of disc is concavo-convex, allowing for both the mandibular fossa and articular tubercle
2) lower surface is concave to receive the mandible
3) the disc is thinner centrally and thicker at the edge

Question 17

What supports the TMJ

Answer 17

The joint is supported by a series of ligaments

Question 18

What is the strongest ligament of the TMJ and what is its function

Answer 18

The Lateral Temporomandibular Ligament

Functions to prevent dislocation of the TMJ

Question 19

Describe the anatomical course of the lateral temporomandibular ligament

Answer 19

Lies laterally and has deep fibers blending with the capsule (for strength)

Runs from the lower border of the zygoma to the posterior border of the neck and ramus of the mandible

Question 20

What other 2 ligaments are attached to the capsule and what is their function?

Answer 20

2 Medial ligaments also strengthen the capsule

Question 21

What 2 accessory ligaments are found in the TMJ? (not attached to capsule)

Answer 21

1) Sphenomandibular ligament
2) Stylomandibular ligament

Question 22

Describe the anatomical course and the function of the Sphenomandibular ligament

Answer 22

Runs from the spine of the sphenoid to the Lingula

It prevents inferior dislocation of the TMJ as it remains at a constant length and tension for all positions of the mandible

Question 23

Describe the anatomical course and the function of the Stylomandibular ligament

Answer 23

Extends from the apex of the styloid process to the posterior ramus of the mandible

It is a thickening of the deep parotid fascia, and hence functions to separate the parotid gland from the submandibular gland

Question 24

When is the jaw least stable?

What does this mean for dislocation of the jaw?

Answer 24

When open

Dislocation of the jaw tends to occur when jaw is open

Question 25

Closing the jaw brings what two surfaces togther?

Answer 25

Closing brings the mandibular condyle into contact with the mandibular fossa

Question 26

When the jaw is closed what contributes to stabilisation?

Answer 26

Occlusion of the teeth

Question 27

What limits displacement of the jaw in the following directions: 1) posterior 2) anterior 3) Inferior

Answer 27

Posterior displacement: is limited by the posterior glenoid tubercle Anterior displacement: is limited by the articular tubercle Inferior dislocation: is prevented by the Sphenomandibular and Stylomandibular ligaments

Question 28

What is the most common dislocation of the jaw and why?

Answer 28

Anterior dislocation because it is possible to slide over the articular tuburcle

Question 29

What 2 groups of muscles move the mandible and where does movement occur?

Answer 29

Move the mandible = muscles of mastication and the hyoid muscles Occurs at = the TMJ

Question 30

Compare the movements that occur in the superior vs Inferior cavity

Answer 30

Superior cavity produces protrusion and retraction Inferior cavity produces elevation and depression

Question 31

How do we produce a lateral movement? (eg. for chewing) Which cavity does this occur in?

Answer 31

This is achieved by alternately protruding and retracting the mandible on each side Therefore occurs in the superior cavity

Question 32

Describe the 3 things that permit active opening of the mouth

Answer 32

1) Gravity 2) The condyles are pulled forwards by the lateral Pterygoid muscles (3). This occurs in the upper cavity 3) The chin is pulled down and back by the digastric muscles in the lower joint cavity (Note: digastric itself is not a prime mover for jaw opening)

Question 33

Describe the two things that permit closing of the jaw

Answer 33

1) Retraction of the mandible: posterior fibers of temporalis (1) pull the mandible backwards (acting at the superior joint cavity) 2) Elevation of the mandible: acts at the inferior joint cavity, via the rest of the temporalis (1), the masseter (2) and the medial Pterygoid (4)

Question 34

List the 4 muscles of mastication and the action of each

Answer 34

Question 35

What is the only muscle which protracts the mandible?

Answer 35

The LATERAL ptyerygoid

Question 36

Give 4 disorders of the TMJ

Answer 36

1) Bruxism: grinding of the teeth 2) Temporomandibular joint pain 3) Mal- occlusion syndromes: misalignment of the teeth 4) Dislocation

Question 37

What can NOT be done when you have a dislocated jaw and how you you fix it?

Answer 37

Shut mouth We must push the condylar head of the mandible back underneath the articular tubercle by exterting pressure 'down and back' at the back of the jaw (inside the mouth)

Question 38

What is the the infratemporal fossa and what is its anatomical location?

Answer 38

An irregular shaped cavity which lies beneath the base of the skull between the pharynx and the ramus of the mandible

Question 39

Give 3 close anatomical relations of the infratemporal fossa

Answer 39

1) below the middle cranial fossa 2) medial and deep to the zygomatic arch 3) behind the maxilla

Question 40

What is the clinical significance of the infratemporal fossa?

Answer 40

It is a site containing many nerves and vessels where procedures may be performed

Question 41

There is an interval present between the zygomatic arch and the cranial bones, what does this allow?

Answer 41

Communication with the temporal fossa

Question 42

What shape is the Infratemporal fossa and what forms its boundries?

Answer 42

The fossa has a wedge shape, its boundaries are formed by bone and soft tissue

Question 43

What are the boundries of the infratemporal fossa? (lateral, medial, anterior, posterior floor and roof)

Answer 43

Lateral: The ramus of the mandible Medial: lateral pterygoid plate of the sphenoid Anterior: posterior surface of maxilla Posterior: the carotid Sheath Floor: medial pterygoid muscle Roof: Greater wing of sphenoid

Question 44

What are the contents of the infratemporal fossa?

Answer 44

1) Muscles of mastication: lateral and medial pterygoid muscles 2) Nerves: * branches of the mandibular nerve (V3) * parasympathetic otic ganglion * chorda tympani (branch of the facial nerve (VII). 3) Artery: maxillary artery and its branch - middle meningeal artery 4) Veins: pterygoid venous plexus

Question 45

What 2 nerve blocks can be administed via the infratemporal fossa?

Answer 45

1) Mandibular Nerve Block: * anaesthetic is infiltrated around the mandibular nerve as it enters the ITF * affects the inferior alveolar, lingual, buccal and auriclotemporal nerves 2) Inferior Alveolar Nerve Block: * sometimes used in dental treatment * anaesthetic is injected around the mandibular foramen to anaesthetise the mandibular teeth, and the lowerlip

Question 46

The infratemporal fossa is a 'potential space', what is the clinical implication of this?

Answer 46

Tumors can sometimes grow for some time without becoming symptomatic. As a result they may be advanced at presentation

Question 47

How may problems with the TMJ present in a patient

Answer 47

As ear pain!