TEMPOROMANDIBULAR JOINT

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Temporomandibular joint

Type
- Synovial
- Condylar type
Articular surfaces
- Upper articular surfaces :
  - Articular tubercle
  - Anterior part of mandibular fossa
  - Posterior non articular part formed by tympanic plate
- Inferior articular surface is formed by head of mandible
Coverings
- Covered with fibrocartilage
Cavity
- Joint cavity divided by intraarticular disc
  - Upper and
  - Lower part
Ligaments
- Fibrous capsule
  - Attached
  - Above to articular tubercle , circumference of mandibular fossa infront and squamotympanic fissure behind
  - Below
    - Neck of mandible
  - Capsule
    - Loose above intra articular disc and tight below it
    - Synovial membrane lines the fibrous capsule and neck of mandible
- Lateral temporomandibular ligament
  - Reinforces and strengthens lateral part of capsular ligament
  - Fibres directed downwards and backwards
  - Attached
    - above to articular tubercle
    - Below to posterolateral aspect of neck of mandible
- Sphenomandibular ligament
  - Accesory ligament
  - Lies in a deep plane away from fibrous capsule
  - Attached superiorly to spine of sphenoid
  - Inferiorly to lingula of mandibular foramen
  - Remnant of meckels cartilage
  - Relations.
    - Medial
      - Chorda tympani nerve
      - Wall of pharynx
    - Lateral
      - Lateral pterygoid muscle
      - Auriculotemporal nerve
      - Maxillary artery
- Stylomandibular ligament
  - Accesory ligament of the joint
  - Thickened part of deep cervical fascia
    - Separates parotid and submandibular salivary glands
  - Attached above to lateral surface of styloid process
  - Below to angle and adjacent part of posterior border of ramus of mandible
ARTICULAR DISC
- oval fibrous plate
- Upper compartment
  - Gliding
- Lower compartment
  - Rotatory and gliding
- Surface
  - Concavo convex superior surface
  - Concave inferior surface
- Attachment
  - Periphery attached to fibrous capsule
Disc
- Anterior extension
- Anterior thick band
- Intermediate zone
- Posterior thick band
- Bilaminar region
- Represents degenerated primitive insertion of lateral pterygoid
Function
- Prevents friction between articulating surface
- Acts as a cushion , helps in shock absorption
- Stabilises condyle by filling up space between articulating surface
RELATIONS OF TMJ
- Lateral
  - Skin and fascia
  - Parotid gland
  - Temporal branches of facial nerve
- Medial
  - Tympanic plate separates the joint from internal carotid artery
  - Spine of sphenoid with upper end of sphenomandibular ligament
  - Auriculotemporal and chorda tympani nerves
  - Middle meningeal artery
- Anterior
  - Lateral pterygoid
  - Masseteric nerve and artery
- Posterior
  - Parotid gland separates joint from external auditory meatus
  - Superficial temporal vessels
  - Auriculotemporal nerve
- Superior
  - Middle cranial fossa
  - Middle meningeal vessels
- Inferior
  - Maxillary artery
  - Maxillary vein
BLOOD SUPPLY
NERVE SUPPLY
MOVEMENTS
- depression ( open mouth )
- Elevation ( closed mouth )
- Protrusion ( protraction of chin )
- Retrusion ( retraction of chin )
- Lateral or side to side movements ( chewing or grinding )

Articular surfaces	Temporal bone: Mandibular fossa and articular tubercle
	Mandible: Condylar process
Main components	Joint capsule
Synovial membrane	Synovial membrane
	Articular disc (anterior/posterior bands, intermediate zone)
Ligaments	Major: Lateral temporomandibular ligament (thickened lateral portion of capsule, strengthens TMJ laterally)
	Minor: Stylomandibular ligament, sphenomandibular ligament
Cavities	Superior (discotemporal) cavity (translational movement)
	Inferior (discomandibular) cavity (rotational movement)
Rotational movements	Elevation: Temporalis, masseter and medial pterygoid muscles
	Depression: Lateral pterygoid, digastric, geniohyoid and mylohyoid muscles
Translational movements	Protrusion: Lateral pterygoid, medial pterygoid muscle, masseter
	Retraction: Posterior fibers of temporalis, deep part of masseter
	Lateral deviation (left or right): Posterior fibers of temporalis, digastric, mylohyoid and geniohyoid muscles (ipsilateral movement); lateral and medial pterygoid muscles (contralateral movement)