Condylar variety
Articular Surfaces
Upper articular surface
Articular tubercle
Anterior part of mandibular fossa
Posterior non-articular part formed by tympanic plate
Inferior articular surface
Head of mandible
Articular surface covered with fibrocartilage
Joint cavity is divided into upper & lower compartments by intra-articular disc
Ligaments
Fibrous capsule
Lateral temporomandibular ligament
Sphenomandibular ligament
Stylomandibular ligament
Fibrous capsule
Attachment
above – articular tubercle
In front - Circumference of mandibular fossa
behind – squamotympanic fissure
below – neck of mandible
Loose above the intra-articular disc
Tight below the disc
Synovial membrane lines the capsule
Lateral temporomandibular ligament
Reinforces & strengthens the lateral part of capsule
Attachment
Above – articular tubercle
Below – posterolateral aspect of neck of mandible
Sphenomandibular ligament
Accessory ligament
Attachment
Superiorly – spine of sphenoid
Inferiorly – lingula of mandibular foramen
Remnant of dorsal part of Meckel’s cartilage
Relations
Laterally –
lateral pterygoid muscle
Auriculotemporal N
Maxillary A
Medially –
chorda tympani N
wall of pharynx
Near its lower end pierced by mylohyoid N & Vessels
Stylomandibular ligament
Accessory ligament
Thickened by deep cervical fascia
Attachment
Above – lateral surface of styloid process
Below – angle & adjacent part of posterior border of mandible
Articular disc
Oval shaped
Fibrous plate
Divides joint cavity into upper & lower compartments
Upper compartment permits gliding movements
Lower compartments permits rotatory & gliding movements
Concavo-convex superior surface
Concave inferior surface
Periphery attached to capsule
Parts
Anterior extension
Anterior thick band
Intermediate zone
Posterior thick band
Bilaminar region containing venous plexus
Represents degenerated primitive insertion of lateral pterygoid
Functions
Acts as cushion
Prevents friction b/n articular surface
Shock absorption
Proprioceptive fibres help to regulate movements
Distribution of weight across TMJ
Relations
Lateral
skin
parotid gland
temporal br of facial N
Medial
tympanic plate separates joint from internal carotid A
spine of sphenoid
upper end of sphenomandibular ligament
auriculotemporal N
chordatympani N
middle meningeal A
Anterior
lateral pterygoid
masseteric N & vsl
Posterior
parotid gland
External acoustic meatus
superficial temporal vsl
auriculotemporal N
Superior
middle cranial fossa
middle meningeal vsl
Inferior
maxillary A & V
Blood supply
Maxillary A & V
Nerve supply
Auriculotemporal N
Masseteric N
Movements
Depression – open mouth
Elevation – closed mouth
Protrusion – protraction of chin
Retrusion – retraction of chin
Lateral/ side to side movement in chewing or grinding
Protraction & Retraction
Occurs in upper compartment
Articular disc + head of mandible glides forwards over upper articular surface
Reversal action occurs in retraction
Axis – horizontal axis connecting two condyles
Depression
Slight opening
The head of mandible moves on the undersurface of disc like a hinge in lower compartment
Axis – vertical axis passing through condyle & posterior border of ramus of mandible
Wide opening
Hinge like movement in lower compartment
Followed by gliding movement in upper compartment as in protraction
At the end of movement, the head lie under the articular tubercle
lateral pterygoid pulls the disc forwards, so movement occurs in both compartments
Side to side movement
Head glides forwards along with disc as in protrusion on one side.
Head of opposite side rotates on vertical axis
Axis – imaginary axis along mid-sagital plane
Chewing of one side
Muscles – medial & lateral pterygoids of opposite side + temporalis & masseter of same side
Dislocation
Occurs during excessive opening of mouth
Head of one side or both slip anteriorly into infratemporal fossa
Results in inability to close the mouth
Reduction done by depressing the jaw at last molar teeth & elevating the chin at the same time
Derangement of articular disc results in overclosure or malocclusion
In operations of TMJ, facial N and auriculotemporal N should be preserved with care.
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