Temporomandibular Articulation Quiz

Temporo-mandibular Articulation

• The temporo-mandibular joint (TMJ) is a diarthrodial, freely movable articulation between the condyle of the mandible and squamous part of the temporal bone.

Classification of Joints

• Fibrous joints: two bones connected by fibrous tissue
• Cartilagenous joints: two bones connected by cartilagenous or bone tissue
• Synovial joints: two bones united and surrounded by a capsule that creates a joint cavity and permits significant movement

TMJ Characteristics

• Bilateral condylar variety of synovial joint
• Anatomically, it is a diarthrodial joint, which is a discontinuous articulation of two bones
• Provides a hinging or rotation movement in one plane, thus can be considered as ginglymoid joint
• Provides a sliding movement, thus called as arthrodial joint
• Therefore, it can be called as GINGLYMOARTHRODIAL joint

Anatomy of TMJ

• Gross Anatomy:
  • Number: present on each side, 2 in number
  • Type: synovial joint
  • Bones involved:
    • Glenoid fossa of temporal bone
    • Condyle of the mandible
• Articulatory system:
  • Upper articular surface: temporal bone
  • Lower articular surface: mandibular condyle
  • Roof: 2 parts of temporal bone
  • Floor: superior surface of disc
  • Articulating surface of mandibular condyle

Articular Surfaces

• Articular surface of temporal bone (Cranial component):
  • Includes three components:
    • Glenoid fossa
    • Postglenoid tubercle
    • Articular eminence
• Articular surface of mandibular condyle (Mandibular component):
  • Ovoid condylar process (head) with narrow mandibular neck
  • Condyle tends to be rounded mediolaterally and convex anteroposteriorly
  • Broad laterally and narrow medially
  • Covered by fibrocartilage

Articular Disc

• Morphology:
  • Derived from mesoderm of 1st pharyngeal arch
  • Biconcave sagitally, thicker anteriorly and thinner posteriorly, oval, avascular, and non-innervated in the middle
  • Can be divided into 3 general regions:
    • Anterior band (2mm)
    • Central intermediate zone (1mm)
    • Posterior band (3 mm)
• Upper joint space is larger (1.2ml)
• Lower joint space is smaller (0.9 ml)

Posterior Disc Attachment/Bilaminar Zone

• Posteriorly: posterior bilaminar zone with rich neurovascular supply
• Disc divides into:
  • Inferior lamella
  • Superior lamella

Function of Articular Disc

• Condyle and the temporal bone do not fit together in the absence of the disk
• Stabilization of the temporomandibular joint
• The articular disc may reduce wear

TMJ Ligaments

• Functional ligaments (True Ligaments):
  • Collateral ligament
  • Capsular ligament
  • Lateral ligament
• Accessory ligaments:
  • Sphenomandibular ligament (remnants of Meckel’s cartilage)
  • Stylomandibular ligament (thick band of deep cervical fascia that limits excessive protrusion of the mandible)