Which structure separates the upper and lower TMJ cavities?

Which structure separates the upper and lower TMJ cavities?

• A. Articular disc
• B. Head of mandible
• C. Mandibular fossa
• D. Articular capsule

Answer: (A)

The articular disc divides the TMJ cavity into two separate synovial spaces, creating a superior and an inferior compartment. This fibrocartilaginous disc sits between the mandibular condyle and the temporal bone’s mandibular fossa, so it acts as a divider rather than a surface for the joint itself. Movements differ by compartment: the upper cavity (between the disc and temporal bone) allows gliding translational movements, while the lower cavity (between the disc and condyle) permits hinge rotation. The other structures—head of the mandible (the condyle) and the mandibular fossa—form the joint surfaces but do not separate the spaces, and the articular capsule surrounds the joint rather than dividing it.

The articular disc divides the TMJ cavity into two separate synovial spaces, creating a superior and an inferior compartment. This fibrocartilaginous disc sits between the mandibular condyle and the temporal bone’s mandibular fossa, so it acts as a divider rather than a surface for the joint itself. Movements differ by compartment: the upper cavity (between the disc and temporal bone) allows gliding translational movements, while the lower cavity (between the disc and condyle) permits hinge rotation. The other structures—head of the mandible (the condyle) and the mandibular fossa—form the joint surfaces but do not separate the spaces, and the articular capsule surrounds the joint rather than dividing it.