Nucleus ambiguus corresponds to which cranial nerve?

• A. IX
• B. X
• C. XI
• D. XII

Answer: (B)

The nucleus ambiguus is the motor nucleus that supplies the muscles of the pharynx, larynx, and soft palate through the cranial nerves IX and X. Among these, the vagus nerve carries the majority of those motor fibers to the pharyngeal and laryngeal muscles, so for a single-cranial-nerve association, this nucleus is most closely linked with the vagus. Damage to this area typically produces problems with swallowing and voice, which align with CN X functions. The glossopharyngeal nerve does contribute some motor input (e.g., to a pharyngeal muscle), but the main efferent output to the important pharyngeal–laryngeal muscles comes from the vagus. Spinal accessory and hypoglossal have separate nuclei and pathways, not the nucleus ambiguus, so they’re not the primary associations here.