Which cranial nerve initiates the pharyngeal swallow?

• A. Trigeminal nerve (CN V)
• B. Glossopharyngeal nerve (CN IX)
• C. Facial nerve (CN VII)
• D. Vagus nerve (CN X)

Answer: (B)

The pharyngeal swallow is triggered by sensory input from the oropharynx. The glossopharyngeal nerve (CN IX) carries that afferent information to the brainstem swallowing center, which then initiates the pharyngeal phase. From there, the actual movement of the pharyngeal muscles is carried out primarily by the vagus nerve (CN X), but the initiating trigger comes from CN IX. Other nerves play different roles: the trigeminal nerve contributes some oral sensation but is not the primary trigger for initiating the pharyngeal swallow; the facial nerve handles facial muscles and taste from the anterior tongue; CN X is the motor driver of the swallow, not the trigger.