The hypoglossal nerve (XII) is primarily responsible for which function?

• A. Tongue movement
• B. Taste
• C. General sensation
• D. Eye movement

Answer: (A)

The hypoglossal nerve is the motor driver for the tongue. It carries somatic motor fibers to all intrinsic tongue muscles and to the extrinsic muscles that move the tongue (genioglossus, hyoglossus, styloglossus, and the intrinsic muscles), enabling actions like protrusion, retraction, and shaping of the tongue that are essential for speech and swallowing. Palatoglossus is an exception, being innervated by the vagus nerve instead of XII, but the rest of the tongue muscles rely on this nerve.

Taste is carried mainly by other cranial nerves: the facial nerve via the chorda tympani for the anterior two‑thirds of the tongue, and the glossopharyngeal nerve for the posterior one‑third, with the vagus contributing to taste in areas like the epiglottis. General sensation to the tongue also comes from other nerves—trigeminal for the anterior two‑thirds, glossopharyngeal for the posterior part, and vagus for specific regions—while eye movement is controlled by the oculomotor, trochlear, and abducens nerves. Thus, the primary function of this nerve is tongue movement.