Neurology | Hypoglossal Nerve: Cranial Nerve XII

📚 Premium Notes & Illustrations for Hypoglossal Nerve (CN XII): https://www.ninjanerd.org/lecture/hypoglossal-nerve-cranial-nerve-xii

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Join us in this lecture, where Professor Zach Murphy will discuss the anatomy and function of the hypoglossal nerve, cranial nerve XII. We begin with its origin from the hypoglossal nucleus in the medulla oblongata and follow its course as it exits the skull through the hypoglossal canal. The lecture explores how this purely motor nerve supplies all intrinsic and most extrinsic muscles of the tongue, except the palatoglossus muscle (innervated by the vagus nerve).

We discuss the specific functions of the hypoglossal nerve in controlling tongue movement for speech, swallowing, and food manipulation. We also cover in detail the role of its extrinsic muscles—genioglossus, hyoglossus, and styloglossus—and the fine motor control provided by intrinsic muscles to change tongue shape.

Additional emphasis is placed on clinical assessment of cranial nerve XII, including tongue protrusion testing and how unilateral lesions cause tongue deviation toward the side of the lesion due to unopposed genioglossus action. The lecture also touches on possible injury mechanisms, such as carotid endarterectomy complications, tumors, or trauma, and the functional deficits they may cause.

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