Which cranial nerve provides motor innervation to the intrinsic and extrinsic tongue muscles?

Which cranial nerve provides motor innervation to the intrinsic and extrinsic tongue muscles?

• A. Trigeminal (CN V)
• B. Facial (CN VII)
• C. Glossopharyngeal (CN IX)
• D. Hypoglossal (CN XII)

Answer: (D)

Motor control of the tongue is provided by a single nerve that supplies all tongue muscles. The hypoglossal nerve innervates both intrinsic tongue muscles, which shape the tongue, and extrinsic tongue muscles, which move it (such as protrusion by the genioglossus and depression or retraction by other tongue muscles). Other cranial nerves may influence related functions like mastication or facial expression, but they do not supply the tongue muscles for movement. Clinically, a lesion to this nerve causes weakness on the same side, with the tongue deviating toward that side when it protrudes. This makes the hypoglossal nerve the correct choice.

Motor control of the tongue is provided by a single nerve that supplies all tongue muscles. The hypoglossal nerve innervates both intrinsic tongue muscles, which shape the tongue, and extrinsic tongue muscles, which move it (such as protrusion by the genioglossus and depression or retraction by other tongue muscles). Other cranial nerves may influence related functions like mastication or facial expression, but they do not supply the tongue muscles for movement. Clinically, a lesion to this nerve causes weakness on the same side, with the tongue deviating toward that side when it protrudes. This makes the hypoglossal nerve the correct choice.