Final answer:
The initial movement of the mandible when opening the mouth is a combination of downward hinging and anterior gliding, allowing the TMJ to function smoothly for mandibular depression.
Step-by-step explanation:
The temporomandibular joint (TMJ) is crucial for the motion of opening and closing the mouth. The initial movement of the mandible during opening is a combination of two actions: downward hinging of the mandible and an anterior gliding motion. This coordinated movement allows the mandibular condyle and articular disc to glide forward from the mandibular fossa onto the articular tubercle, ultimately resulting in a forward and downward motion of the condyle leading to mandibular depression.