Which muscle is crucial for controlling the movement of the TMJ disc?

The lateral pterygoid muscle plays a critical role in controlling the movement of the temporomandibular joint (TMJ) disc. This muscle is primarily responsible for the forward and downward movements of the mandible, which includes protraction (moving the jaw forward) and helping in the opening of the mouth. When the lateral pterygoid muscle contracts, it helps stabilize the disc that sits within the temporomandibular joint during movements. It has two heads: the superior head helps to stabilize the disc during jaw movements, while the inferior head is more involved in the movement of the mandible itself.

In contrast, the temporalis muscle is primarily responsible for the elevation and retraction of the mandible, providing strength during biting and chewing. The masseter muscle, while also a powerful muscle for jaw closure and elevation, does not play a significant role in the control of the TMJ disc's position. The digastric muscle assists in depression of the mandible and aids in swallowing, but it is not directly involved in the control of the TMJ disc. Therefore, the lateral pterygoid muscle is uniquely situated to play this crucial role in disc movement and stabilization at the TMJ.