Which cranial nerve is responsible for tongue movement?

• A. I Olfactory
• B. II Optic
• C. IX Glossopharyngeal
• D. XII Hypoglossal

Answer: (D)

Tongue movement is controlled by motor innervation to the tongue muscles, which comes from the hypoglossal nerve. It supplies all the intrinsic tongue muscles and most of the extrinsic muscles (such as genioglossus, hyoglossus, and styloglossus), enabling actions like protrusion, retraction, and shaping the tongue for speech and swallowing. If this nerve is damaged on one side, the tongue will deviate toward that side when you try to protrude it, due to weakness of the muscles on that side.

The other nerves listed do not primarily control tongue movement: the olfactory nerve handles smell, the optic nerve handles vision, and the glossopharyngeal nerve mainly supplies taste and some pharyngeal muscles involved in swallowing.