Which nerve supplies the stylopharyngeus muscle?

• A. CN X
• B. CN VII
• C. CN IX
• D. CN XII

Answer: (C)

The stylopharyngeus is a pharyngeal muscle that elevates the pharynx during swallowing, and its motor innervation comes from the glossopharyngeal nerve. This muscle derives from the third pharyngeal arch, and CN IX provides the branchial motor fibers to it, allowing it to contract and lift the pharynx. The vagus nerve supplies many other pharyngeal muscles, but stylopharyngeus is uniquely innervated by CN IX, while the hypoglossal nerve (CN XII) controls tongue muscles and the facial nerve (CN VII) handles facial muscles and stapedius. So CN IX is the correct nerve for stylopharyngeus.