Which cranial nerve is responsible for the ability to pucker and smile?

The cranial nerve responsible for the ability to pucker and smile is the facial nerve, also known as cranial nerve VII. This nerve innervates the muscles of facial expression, allowing for a variety of movements such as smiling, frowning, and puckering the lips. The motor function of the facial nerve enables the coordination of these complex movements, which are essential for nonverbal communication and emotional expression.

In contrast, other cranial nerves mentioned serve different functions. For instance, cranial nerve V, known as the trigeminal nerve, is primarily involved in sensation to the face and controlling muscles used for chewing, not facial expressions. Cranial nerve IX, the glossopharyngeal nerve, is involved in taste and swallowing functions, whereas cranial nerve XII, the hypoglossal nerve, controls tongue movements. Thus, their roles do not relate directly to the facial expressions required for puckering and smiling.