What action does the hypoglossal nerve primarily control?

The hypoglossal nerve is primarily responsible for controlling motor function to the tongue. This cranial nerve, known as cranial nerve XII, innervates the intrinsic and extrinsic muscles of the tongue, which are essential for movements such as speaking, swallowing, and manipulating food within the oral cavity. The precise control over tongue movements is critical for articulation of speech sounds and effective swallowing, making the hypoglossal nerve vital for these functions.

In contrast, the other options provided do not pertain to the action of the hypoglossal nerve. Eye movement is controlled by several other cranial nerves, specifically those responsible for innervating the extraocular muscles. Facial expressions are managed by the facial nerve. Swallowing involves coordination of several muscles and nerves, including the vagus and glossopharyngeal nerves, but it is not specifically under the control of the hypoglossal nerve.