Which muscle is the only muscle innervated solely by CN IX?

Which muscle is the only muscle innervated solely by CN IX?

• A. Stylopharyngeus
• B. Palatopharyngeus
• C. Salpingopharyngeus
• D. Superior constrictor

Answer: (A)

The key idea is that most pharyngeal muscles get their motor supply from the pharyngeal plexus, which is from the vagus nerve (CN X). Only one pharyngeal muscle receives direct innervation from CN IX. Stylopharyngeus stands out because it is the sole pharyngeal muscle innervated by glossopharyngeal nerve. It runs from the styloid process to the pharyngeal wall and functions to elevate the pharynx (and larynx) during swallowing. This direct IX innervation explains why it remains unique among the pharyngeal muscles, whereas palatopharyngeus, salpingopharyngeus, and the superior constrictor are all innervated via the pharyngeal plexus from CN X.

The key idea is that most pharyngeal muscles get their motor supply from the pharyngeal plexus, which is from the vagus nerve (CN X). Only one pharyngeal muscle receives direct innervation from CN IX.

Stylopharyngeus stands out because it is the sole pharyngeal muscle innervated by glossopharyngeal nerve. It runs from the styloid process to the pharyngeal wall and functions to elevate the pharynx (and larynx) during swallowing. This direct IX innervation explains why it remains unique among the pharyngeal muscles, whereas palatopharyngeus, salpingopharyngeus, and the superior constrictor are all innervated via the pharyngeal plexus from CN X.