Free A Spinal Exam 4 Practice 2026 - Free Practice Questions and Study Guide

The structure that separates the upper and lower cavities of the TMJ is the articular disc. This fibrocartilaginous disc sits between the mandibular condyle and the temporal bone, dividing the joint into two synovial spaces: the upper compartment (between the disc and the temporal bone) and the lower compartment (between the disc and the condyle). This separation is essential because different parts of the jaw move in different ways: the upper compartment mainly allows gliding movements, while the lower compartment primarily enables hinge movements.

In addition, the disc is connected anteriorly to the lateral pterygoid muscle and posteriorly to the capsule and retrodiscal tissue, helping it stay in place and function as a divider within the joint. The joint capsule surrounds the entire joint, and the mandibular fossa and the head of the mandible (condyle) are the bony components that form part of the joint, but they do not serve to separate the two cavities.