Which branch of the facial nerve is mainly responsible for lacrimation?

• A. GSPN
• B. Chorda tympani
• C. Both equally
• D. None of the above

Answer: (A)

Lacrimation is driven by parasympathetic fibers traveling with the greater petrosal nerve, a branch of the facial nerve. These preganglionic fibers originate in the superior salivatory nucleus and reach the pterygopalatine ganglion via the greater petrosal nerve, where they synapse. The postganglionic fibers then reach the lacrimal gland by hitchhiking with branches of the maxillary division (V2): they ride along the zygomatic nerve and then via the zygomaticotemporal connection to the lacrimal nerve, which supplies the lacrimal gland. The chorda tympani, by contrast, carries taste fibers and parasympathetic nerves to the submandibular and sublingual glands, not to the lacrimal gland, so it isn’t the main route for tear production. In short, the greater petrosal nerve is the principal channel for lacrimal gland innervation through its parasympathetic pathway.