Final answer:
The mandibular arch is movable through the action of the temporomandibular joint (TMJ).
Step-by-step explanation:
The temporomandibular joint (TMJ) is the joint that allows for opening (mandibular depression) and closing (mandibular elevation) of the mouth, as well as side-to-side and protraction/retraction motions of the lower jaw. This joint involves the articulation between the mandibular fossa and articular tubercle of the temporal bone, with the condyle (head) of the mandible. Located between these bony structures, filling the gap between the skull and mandible, is a flexible articular disc. This disc serves to smooth the movements between the temporal bone and mandibular condyle.