Which joint is referred to as the "upper" joint in TMJ anatomy?

The concept of the upper joint in TMJ anatomy refers specifically to the joint formed between the articular disc and the temporal bone. This is termed the upper compartment of the TMJ, and it plays a crucial role in the movements of the jaw.

In this joint, the articular disc acts as a cushion between the condyle of the mandible and the temporal bone, allowing for smooth movement, especially during actions such as opening and closing the mouth. The movement that occurs here is primarily translational as the mandible moves forward or backward. This upper joint is critical for the proper function of the TMJ as it helps in various activities, including chewing, speaking, and other jaw movements.

Understanding the anatomy of the TMJ and the characteristics of its joints is essential for diagnosing and treating conditions related to the jaw, such as TMJ disorders, which can lead to pain and dysfunction.