Greater petrosal nerve is a branch of which cranial nerve?

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

Answer: (C)

The key idea is that the greater petrosal nerve carries preganglionic parasympathetic fibers that arise from the facial nerve (cranial nerve VII). Within the temporal bone, a branch of the facial nerve splits off as the greater petrosal nerve, containing these parasympathetic fibers from the superior salivatory nucleus. It then joins with the deep petrosal nerve to form the nerve of the pterygoid canal, guiding these fibers to the pterygopalatine ganglion where they synapse. From there, postganglionic fibers ride with branches of the maxillary nerve to reach targets like the lacrimal gland and nasal mucosa.

The other cranial nerves listed are not sources of the greater petrosal nerve: the glossopharyngeal nerve, vagus nerve, and the trigeminal nerve each have different roles and pathways, with parasympathetic outflow routed through distinct branches (for example, parasympathetic fibers to the parotid gland travel with the lesser petrosal nerve from the glossopharyngeal nerve, not via the greater petrosal).