Which nerves are primarily involved in the pharyngeal phase of swallowing, with possible contributions from the accessory nerve?

• A. Trigeminal (V) and Vagus (X)
• B. Glossopharyngeal (IX) and Vagus (X) with contributions from Accessory XI
• C. Olfactory (I) and Optic (II)
• D. Hypoglossal (XII) and Accessory (XI)

Answer: (B)

The pharyngeal phase is driven by the pharyngeal plexus, with the main motor input coming from the glossopharyngeal and vagus nerves. The glossopharyngeal nerve supplies the stylopharyngeus muscle, which helps lift and widen the pharynx to receive the bolus. The vagus nerve provides motor fibers to most of the pharyngeal constrictors and to muscles of the soft palate through its pharyngeal branches, producing the coordinated constriction that propels the bolus downward. In some cases, the cranial portion of the accessory nerve can join the vagus to contribute to innervation of pharyngeal muscles, hence its potential involvement. Other nerves listed are not the primary drivers of this phase: the trigeminal nerve mainly handles jaw movements and some palate function, while the olfactory and optic nerves carry smell and vision and do not participate in swallowing. The hypoglossal nerve controls tongue movements, which are more about shaping the bolus rather than propelling it through the pharynx.