Which cranial nerve primarily mediates both the intrinsic and extrinsic tongue musculature?

Which cranial nerve primarily mediates both the intrinsic and extrinsic tongue musculature?

• A. Vagus (CN X)
• B. Hypoglossal (CN XII)
• C. Facial (CN VII)
• D. Trigeminal (CN V)

Answer: (B)

The key idea is that motor control of tongue muscles is provided mainly by the hypoglossal nerve. The intrinsic tongue muscles, which shape the tongue, are all innervated by this nerve. The extrinsic tongue muscles that move the tongue as a whole or change its position (such as genioglossus, hyoglossus, and styloglossus) are also primarily innervated by the hypoglossal nerve. The one exception is palatoglossus, which elevates the posterior tongue and is innervated by the vagus nerve via the pharyngeal plexus. Because the hypoglossal nerve supplies the vast majority of tongue muscle motor function, it best mediates both intrinsic and extrinsic tongue musculature. Clinically, a hypoglossal nerve lesion causes tongue weakness with deviation toward the affected side on protrusion and possible fasciculations, affecting bolus formation and propulsion in swallowing. The other nerves don’t provide this broad motor control to both groups of tongue muscles.

The key idea is that motor control of tongue muscles is provided mainly by the hypoglossal nerve. The intrinsic tongue muscles, which shape the tongue, are all innervated by this nerve. The extrinsic tongue muscles that move the tongue as a whole or change its position (such as genioglossus, hyoglossus, and styloglossus) are also primarily innervated by the hypoglossal nerve. The one exception is palatoglossus, which elevates the posterior tongue and is innervated by the vagus nerve via the pharyngeal plexus. Because the hypoglossal nerve supplies the vast majority of tongue muscle motor function, it best mediates both intrinsic and extrinsic tongue musculature. Clinically, a hypoglossal nerve lesion causes tongue weakness with deviation toward the affected side on protrusion and possible fasciculations, affecting bolus formation and propulsion in swallowing. The other nerves don’t provide this broad motor control to both groups of tongue muscles.