The TMJ and Infratemporal Fossa Flashcards
What 2 bones make up the skull?
Cranium + Mandible
In an adult what is the only movable joint?
Temporomandibular Joint
What joins the R and L parts of the mandible?
Midline fibrous joint – mental symphisis
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
a) Condylar Process → articulates with skull
b) Coronoid Process → non-articulating portion
c) Alveolar Process → internal ridge
d) Mental foramen
Label the following parts of the mandible:
- Condylar Process
- Coronoid Process
- Ramus
- Angle
- Body
- Mental foramen
- Alveolar arch
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?
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
Which part of the mandible holds the teeth?
The alveolar process (whole structure = alevolar arch)
What type of joint is the TMJ and therfore what MUST it have?
Describe this and incl what it allows
Synovial joint
Therfore the TMJ has a fibrous capsule which is relatively thin and loose to allow movement, but sacrifices stability
List 2 functions of the TMJ
1) allows articulation between cranium and mandible
2) facilitates jaw movement
List the 3 bony points that articulate in the TMJ and label them on the image below
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
What is the main function of the Articular tubercle?
Prevents jaw from dislocating anteriorly
(it also forms part of the opening of the jaw)
What covers the 2 articulating surfaces of the TMJ?
fibrocartilage
What divides the TMJ into 2 synovial cavities?
Describe the location of each cavity
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
What does having 2 synovial cavities allow for in the TMJ?
allows a wide variety of movement to occur within the joint
Why is articular disc necessary within the TMJ?
Because the bones are poorly aligned so the disc’s shape allows them to fit
Highly mobile joint means the disc provides some stability
Describe the shape of the articular disc in terms of:
1) its upper surface
2) lower surface
3) thickness across the disc
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
What supports the TMJ
The joint is supported by a series of ligaments
What is the strongest ligament of the TMJ and what is its function
The Lateral Temporomandibular Ligament
Functions to prevent dislocation of the TMJ
Describe the anatomical course of the lateral temporomandibular ligament
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
What other 2 ligaments are attached to the capsule and what is their function?
2 Medial ligaments also strengthen the capsule
What 2 accessory ligaments are found in the TMJ? (not attached to capsule)
1) Sphenomandibular ligament
2) Stylomandibular ligament
Describe the anatomical course and the function of the Sphenomandibular ligament
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
Describe the anatomical course and the function of the Stylomandibular ligament
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
When is the jaw least stable?
What does this mean for dislocation of the jaw?
When open
Dislocation of the jaw tends to occur when jaw is open
Closing the jaw brings what two surfaces togther?
Closing brings the mandibular condyle into contact with the mandibular fossa
When the jaw is closed what contributes to stabilisation?
Occlusion of the teeth
What limits displacement of the jaw in the following directions:
1) posterior
2) anterior
3) Inferior
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
What is the most common dislocation of the jaw and why?
Anterior dislocation because it is possible to slide over the articular tuburcle
What 2 groups of muscles move the mandible and where does movement occur?
Move the mandible = muscles of mastication and the hyoid muscles
Occurs at = the TMJ
Compare the movements that occur in the superior vs Inferior cavity
Superior cavity produces protrusion and retraction
Inferior cavity produces elevation and depression
How do we produce a lateral movement? (eg. for chewing)
Which cavity does this occur in?
This is achieved by alternately protruding and retracting the mandible on each side
Therefore occurs in the superior cavity
Describe the 3 things that permit active opening of the mouth
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)
Describe the two things that permit closing of the jaw
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)
List the 4 muscles of mastication and the action of each
What is the only muscle which protracts the mandible?
The LATERAL ptyerygoid
Give 4 disorders of the TMJ
1) Bruxism: grinding of the teeth
2) Temporomandibular joint pain
3) Mal- occlusion syndromes: misalignment of the teeth
4) Dislocation
What can NOT be done when you have a dislocated jaw and how you you fix it?
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)
What is the the infratemporal fossa and what is its anatomical location?
An irregular shaped cavity which lies beneath the base of the skull between the pharynx and the ramus of the mandible
Give 3 close anatomical relations of the infratemporal fossa
1) below the middle cranial fossa
2) medial and deep to the zygomatic arch
3) behind the maxilla
What is the clinical significance of the infratemporal fossa?
It is a site containing many nerves and vessels where procedures may be performed
There is an interval present between the zygomatic arch and the cranial bones, what does this allow?
Communication with the temporal fossa
What shape is the Infratemporal fossa and what forms its boundries?
The fossa has a wedge shape, its boundaries are formed by bone and soft tissue
What are the boundries of the infratemporal fossa?
(lateral, medial, anterior, posterior floor and roof)
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
What are the contents of the infratemporal fossa?
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
What 2 nerve blocks can be administed via the infratemporal fossa?
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
The infratemporal fossa is a ‘potential space’, what is the clinical implication of this?
Tumors can sometimes grow for some time without becoming symptomatic. As a result they may be advanced at presentation
How may problems with the TMJ present in a patient
As ear pain!
