The greater petrosal nerve is a branch of which cranial nerve?

• A. CN VII (Facial nerve)
• B. CN IX (Glossopharyngeal)
• C. CN X (Vagus)
• D. CN V (Trigeminal)

Answer: (A)

The greater petrosal nerve is a branch of the facial nerve (cranial nerve VII). It carries preganglionic parasympathetic fibers that originate in the superior salivatory nucleus and are destined for the lacrimal gland. After leaving the facial nerve in the temporal bone, it combines with the deep petrosal nerve to form the nerve of the pterygoid canal, reaching the pterygopalatine ganglion where it synapses. From there, postganglionic fibers reach the lacrimal gland via pathways that accompany branches of the trigeminal nerve. The glossopharyngeal nerve provides parasympathetic input to the parotid via the lesser petrosal nerve, not the greater petrosal; the vagus nerve does not give rise to a lacrimal pathway, and the trigeminal nerve itself does not carry parasympathetic fibers to lacrimal glands.