Temporomandibular Joint

Definition

-Articulation between mandible and cranium

-Bilateral joint

-right and left joints are connected by mandible, making their movements interdependent 

TMJ

Characteristics

Complexity of motion

-most movements are combinations of 2 types of motion(translation and rotation)

-a synovial joint subdivided into 2 compartments y an articular disc.

TMJ

Bony Components 

Temporal Bone

-Mandibular (glenoid) fossa

-Articular tubercle

-Articular eminence

-Postglenoid tubercle (spine)

Mandibular condyle 

TMJ

Soft tissue components

-Joint capsule

-Synovial membrane

Articular Disc

Composition, Major parts, Compartments 

-Composed of Fibrous tissue changing to fibrocartilage in older adults

-Major parts: anterior and posterior bands, intermediate zone

-Divides joint into upper and lower compartments

Articular Disc

Attachments

-Medial and lateral poles of condyle

-Posterior wall of joint capsule via retrodiscal pad

-Anterior wall of joint capsule and superior head of lateral pterygoid muscle 

Bilaminar Zone

(Retrodiscal Pad)

-Inferior lamina: collagenous fibers running down ot attach to posterior condylar neck

-Superior lamina: some collagenous fibers interspersed with numerous elastic fibers; attaches to typmanic plate and mandibular fossa

TMJ

Ligaments

-Lateral ligament (temporomandibular ligament)

-Sphenomandibular ligament

-Stylomandibular ligament

TMJ 

Nerve supply

TMJ

blood supply

-superficial temporal a

-branches of maxillary a. around it

TMJ

Types of movement

-Translation: (grinding) in superior joint compartment(disc-eminence)

-Rotation: (hinge) in inferior joint compartment (disc-condyle) 

-movements of the disc during opening and closing 

-result of the combined action of several mm. contracting simultaneously or in a coordinated sequence 

-movements

1.Elevation(closing of mouth)

2.Depression(openeing of mouth)

3.Lateral movements(side-to-side)

-Temporalis

-Masseter

-Medial pterygoid

-Masseter and medial pterygoid form "pterygomassetric sling" under the angle of the mandible

-Inferior head of the lateral pterygoid

-Digastric (pulls downward and backwards on the mandibular symphysis) 

-MM. acting unilaterally

-Contralateral excursion: medial and lateral pterygoid

-Ipsilateral movement: masseter and temporalis