The Temporomandibular Joint Flashcards Preview

ESA 4 - Head and Neck > The Temporomandibular Joint > Flashcards

Flashcards in The Temporomandibular Joint Deck (20)
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1
Q

What is the temporomandibular joint?

A

It is the joint formed by articulation if the mandible with the cranium

Also known as the mandibular joint or jaw-joint

It is found anterior and roughly level to the tragus of the ear

It is the most complex joint in the body

2
Q

What are the articular surfaces of the temporomandibular joint?

A

Superior
- On the under surface if the squamous part of the
temporal bone, there are 2 articular sites with sinuous
cross-sectional presentation
- Mandibular fossa (posterior and concave)
- Articular fossa (anterior and convex)

Inferior
- The condyle of the mandible had a rounded superior
edge & ellipsoid circumference with it’s major axis
postero-medial

3
Q

What type of joint is the temporormandibular joint?

A

Synovial

4
Q

What are the features of the TMJ capsule?

A

It has a fibrous capsule

The capsule is very strong in itself

The capsule is also very thin and loose to permit movements of the joint

Capsular attachments
Superiorly
- The circumference of the mandibular fossa and
articular tubercle
Inferiorly
- The neck of the condyle of the mandible

It is strengthened by extracapsular ligaments, one lateral and two medial

It remains liable to subluxation or complete displacement owing to its looseness

5
Q

Does direct bone-to-bone articulation occur in the TMJ?

A

No.

A fibrous disc known as the articular disc or meniscus separates bony surfaces from making direct contact

This creates 2 cavities within the TMJ capsule - an upper and lower capsule

6
Q

What do the two cavities of the TMJ allow?

A

Two separate types of movement (or displacement) of the joint

  • A gliding joint (translational movement in the upper
    cavity)
  • A modified hinge joint (rotational movements in the
    lower cavity)
7
Q

What are the articular surfaces of the upper cavity of the TMJ?

A

Articulating surfaces are:
- Articular surface of the under surface if the temporal
bone
- Upper surface of the articular disc

8
Q

What are the articular surfaces of the lower cavity of the TMJ

A

Articulating surfaces are:

  • The mandibular condyle
  • Inferior surface of the articular disc
9
Q

Describe the congruity between the articulatory surfaces of the TMJ

A

The superior and inferior articular surfaces are incongruous

Superior surface
- Convexo-concave (antero-posteriorly)
Inferior surface
- Condyloid with an oblique trajectory superiorly

The articular disc between bony articular surfaces makes them congruent

10
Q

What are the articulatory surfaces of the TMJ lined with?

A

Fibrocartilage

11
Q

Describe the articular disc in the TMJ

A

It is composed of dense fibrous connective tissue

It has the same composition as the fibrocartilage lining the articulatory surfaces

Upper surface is concavo-convex (antero-posteriorly) to fit both the mandibular fossa and articular tubercle

Inferior surface is concave for reception of the mandibular condyle

It is thicker at its periphery where it attaches to the articular capsule

It can recoil or stretch a little with movement

It is thinner centrally

And it makes the articulating surfaces congruent

12
Q

How does the inferior bony articulatory surface of the TMJ Move and work?

A

It is condyloid

Its surface area is significantly lower than its superior counterpart

It can move anteriorly to articulate with anterior superior articular surface

This movement is known as translation or protrusion

Translational movements of the condyle are in an oblique plane

When the jaw is closed, it articulates with the posterior superior articular surface

Rotational movements occur when the condyle is engaged in the concavity of the posterior superior articular surface.

13
Q

What are the extracapsular ligaments of the TMJ?

A

One lateral ligament:
Temporomandibular ligament:
- The strongest ligament of the TMJ
- Its deep fibres blend with the capsule
- Attachment: - Lower border of zygoma to posterior
border of neck & ramus of mandible
- It tightens the head in retrusion (closing & pulling jaw
backwards)

And two medial ligaments that strengthen the capsule, but they are less significant

14
Q

What are the accessory ligaments of the TMJ?

A

Sphenomandibular ligament:
- It remains constant in length and tension for all
positions of the mandible
- It prevents inferior dislocation of the joint
- It goes from the spine of the sphenoid bone to the
mandibular foramen

Stylomandibular ligament:
- It extends from near the apex of the styloid process
to the posterior border of the ramus of the mandible
near its angle
- It is a thickening of the deep parotid fascia
- It separates the parotid gland from the submandibular
gland

15
Q

When is the TMJ the most stable?

A

When the jaw is closed
The mandibular condyle is in contact with mandibular fossa
Teeth are in occlussal contact
Perfect occlusion further stabilises the joint

Least stable when the jaw is open

16
Q

What are the movements of the TMJ and what is displaced?

A

It is always the mandible that is displaced in order for movements to occur

Movements occur by displacements in the:

  • Superior joint cavity (gliding)
    • Protrusion and retraction
  • Inferior joint cavity (hinge)
    • Depression of the mandible
    • Elevation of the mandible
17
Q

How is the TMJ opened? (opening of jaw)

A

It is a simple movement

The condyles are pulled forwards - protrusion

  • Gliding movement
  • Lateral pterygoid muscles (3)
  • Upper joint cavity

The chin is pulled down and back

  • Hinge movement
  • Digastric muscles
  • Lower joint cavity

Digastric is not a prime mover for jaw opening

18
Q

How is the TMJ closed? (closing of jaw)

A

Retraction of mandible
- Posterior fibres of the temporalis muscle pull the
mandible backwards
- (Superior joint cavity)

Elevation of the mandible

  • Remainder of temporalis muscle
  • Masseter muscles (all its layers)
  • Medial pterygoid muscles
  • (Inferior joint cavity)
19
Q

What are the anatomical factors aiding stability of the TMJ?

A

Posterior displacement of the joint is limited by the post glenoid tubercle

Passive anterior displacement of the joint is limited by the articular tubercle

Inferior dislocation is prevented by the:

  • Sphenomandibular ligament - (internal lateral)
  • Stylomandibular ligament - (posteriorly)
20
Q

What are some common disorder of TMJ?

A

Bruxism (grinding teeth when asleep)

Temporomandibular pain dysfunction disorders (muscular pain)

Mal-occlusion syndromes (muscular pain)