What are the structural components of TMJ?
- Squamous part of temporal bone
- Condylar head of mandible
- Articular disc
- Contained within the TMJ (between temporal and mandible)
- Ligaments
TMJ joint classifiication
Ginglymoarthrodial joint
- Articular disc divides joint into upper and lower
- Gliding - upper
- Translation
- Protrusion/protraction; retrusion/retraction
- Upper part of joint
- Hinge
- Rotation
- Elevation; depression
- Lower part of joint
- Gliding - upper
- Diarthritic joint - capable of free movement
What kind of cartilage is the mandibular fossa covered with?
How is this different from other articular surfaces in the body?
Where is the cartilage the thickest?
Avascular fibrocartilage
Other joints in body have hyaline cartilage
Thickest in load-bearing areas i.e. squamous portion, disc, condyle
What are anterior, intermediate, posterior relations to the squamous portion of the temporal bone?
- Anterior
- Articular eminence becoming articular tubercle
- Attachment for capsule and lateral (tempromandibular) ligament
- Articular eminence becoming articular tubercle
- Intermediate
- Glenoid (mandibular) fossa
- Depression for condyle
- Thin layer of compact bone
- Glenoid (mandibular) fossa
- Posterior
- Petrotympanic (squamotympanic) fissure
- Tympanic plate tapering to post-glenoid tubercle
- Attachment for capsule and retrodiscal pad
What kind of bone makes up the mandibular condyles?
Cancellous (spongy) covered with a thin layer of compact
What are the mediolateral and anteroposterior measurements of mandibular condyles?
Mediolateral: 20mm
Anteroposterior: 10mm
What is the articular disc comprised of?
Dense fibrous CT
What is unique about the articular disc, in terms of innervation and blood supply?
Avascular and aneural in intermediate portion (high load bearing)
List the articular disc bands in order from thinnest to thickest
Intermediate < Anterior < Posterior
- Anterior
- Thick
- Anterior to condyle with mouth closed
- Intermediate
- Thin
- Along articular eminence with mouth closed
- Posterior
- Thickest portion of the disc
- Superior to condyle with mouth closed
- Attached to bilaminar zone including retrodiscal pad
What are the articular disc attachments?
- Medial/lateral
- Strong collateral attachments
- Attach disc to condyle
- Anterior
- Disc attached to capsule and superior head of lateral pterygoid
- Posterior
- Disc is contiguous with bilaminar zone, blends with the capsule
What is the bilaminar zone?
Bilaminar structure posterior to articular disc
Highly distortable when opening mouth
What is the bilaminar zone composed of?
- Superior lamina
- Elastic fibers
- Anchor suprioer part o posterior disc to the capsule and bone, postglenoid tubercle and tympanic plate
- Retrodiscal pad
- Most vascular and neural portion of TMJ
- Collagen, elastic fibers, fat, nerves, BVs
- Inferior lamina
- Collagen
- Anchors inferior aspect of posterior disc to the capsule
What TMJ compartment secretes synovial fluid?
Synovial membrane, lining TMJ
What are the volumes of the superior and inferior TMJ compartments?
Superior: 1.2mL
Inferior: 0.9mL
Fibrous (joint) capsule or capsular ligament
- Completely encloses the articular surface of temporal bone and condyle
- Sensory receptors
- Outer fibrous layer
- Fibrous CT
- Toughened along medial and lateral aspects by ligaments
- Inner synovial layer
- Lined by highly vascular synovial membrane
What are the different capsule attachments?
- Superior
- Rim of temporal articular surfaces
- Inferior
- Condylar neck
- Medial
- Medial collateral ligament
- Lateral
- Lateral collateral ligament
- Anterior
- Superior head of lateral pterygoid m.
- Posterior
- Retrodiscal pad
Collateral (discal) ligaments
- Medial collateral ligament
- Connects medial articular disc to medial side of condyle
- Lateral collateral ligament
- Connects lateral articular disc to lateral side of condyle
- Called discal ligaments
- Composed of collagenous CT - DO NOT stretch
What are the extracapsular ligaments
Lateral temporomandibular ligament
Stylomomandibular ligament
Sphenomandibular ligament
Lateral temporomandibular ligament
- Closest to the joint
- Just lateral to the capsule, blends with it
- Margin of the articular tubercle to the neck of the mandible
- Prevents lateral displacement of condyle
- 2 separate bands
- Outer oblique
- Largest portion
- Limits opening of mandible
- Inner horizontal
- Smaller band
- Limits posterior movement of articular disc and condyle
- Outer oblique
Sphenomandiblar ligament
- Medial to TMJ
- Spine of sphenoid bone to the lingula
- Remnant of Meckel’s cartilage
- Acts as a pivot on mandible
- Limits max opening of jaw
Stylomandibular ligament
- Styloid process of temporal bone to posterior margin and angle of mandible
- Composed of deep cervical fascia thickening
- Limits anterior protrusion of mandible
- Relaxed when mouth is closed, tense with extreme protrusion
Arterial supply
External Carotid Artery
- Superficial temporal a.
- Maxillary a.
- Deep auricular a.
- Anterior tympanic a.
- Masseteric a.
NOT lingual
TMJ sensory innervation
- Auriculotemporal n.
- Post. division of V3
- Sensory branches to TMJ, capsule
- Primary innervation of TMJ
- Masseteric n.
- Ant. divison of V3
- Sensory to TMJ
- Posterior deep temporal n.
- Ant. division of V3
- Motor to TMJ
m. closing/elevating the mandible
masseteric
medial pterygoid
temporalis
