Which muscles assist with the FIRST (preparatory) movements of mastication — getting food into the mouth and positioning it on the occlusal table?

Correct answer: D. Orbicularis oris and buccinator

• A. Palatoglossus and styloglossus are extrinsic tongue muscles active later, during bolus formation and the oral phase of swallowing — not the initial intake and cheek positioning.
• B. Masseter and temporalis are the primary POWER elevators of the mandible. They act during the crushing and grinding phases, after food has already been positioned.
• C. The pterygoids control protrusion, lateral excursion and the opening cycle — again part of the grinding stroke rather than the initial ingestion.
• D. CORRECT. The first phase of mastication is INGESTION and BOLUS POSITIONING, not power crushing. The ORBICULARIS ORIS closes the lips to seal the oral cavity and draw food in; the BUCCINATOR tenses the cheek and pushes food from the buccal vestibule back onto the occlusal surfaces. Both are muscles of facial expression (CN VII) and both work before the true masticatory muscles generate crushing force.

Note: The buccinator/orbicularis 'oral seal' is also why an incompetent lip seal or a buccinator deficit produces food pocketing in the vestibule.