The facial nerve (cranial nerve VII) controls the muscles responsible for lip movement. It's responsible for both the muscles that elevate and depress the lips, allowing us to smile, frown, pucker, and perform other facial expressions.
- The buccal branch of the facial nerve controls the orbicularis oris muscle, which forms the circular muscle of the mouth, and other muscles responsible for lip elevation.
- The marginal mandibular branch of the facial nerve controls the muscles that depress the lips, enabling us to smile and express different emotions.
The trigeminal nerve (cranial nerve V) provides sensory innervation to the lips, allowing us to feel touch, temperature, and pain. The three branches of the trigeminal nerve are:
- Ophthalmic nerve (V1): Sensory innervation to the forehead, upper eyelid, and cornea.
- Maxillary nerve (V2): Sensory innervation to the cheek, upper lip, and upper teeth.
- Mandibular nerve (V3): Sensory innervation to the lower lip, lower teeth, and chin.
