Which structures are chiefly responsible for forming and controlling the food BOLUS during the oral preparatory phase of swallowing?

Correct answer: A. The tongue, the buccinator and the lips

• A. CORRECT. The TONGUE gathers and shapes the masticated food and mixes it with saliva; the BUCCINATOR tenses the cheek and pushes food medially back onto the occlusal table so it is not lost in the buccal vestibule; and the LIPS (orbicularis oris) provide the anterior seal that stops the bolus escaping. Together they form the mobile container within which the bolus is assembled.
• B. The suprahyoid and infrahyoid muscles elevate and then depress the larynx during the pharyngeal phase of swallowing, again after bolus formation.
• C. The muscles of mastication generate the force that comminutes the food, but they do not gather or contain the bolus.
• D. The soft palate and palatoglossus seal the nasopharynx and initiate the pharyngeal phase — they act AFTER the bolus is formed.

Note: This is exactly why buccinator or facial nerve weakness causes food pocketing in the buccal vestibule, and why a patient with lip incompetence drools and loses bolus anteriorly.