The lip's nerve supply is complex, involving both sensory and motor nerves. Different parts of the lip are innervated by different nerves.
Sensory Innervation: Feeling the Lip
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Upper Lip: The upper lip receives its sensory innervation from the infraorbital branch of the maxillary division of the trigeminal nerve (cranial nerve V2). This nerve carries signals related to touch, temperature, and pain from the upper lip to the brain.
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Lower Lip: The lower lip's sensory information is conveyed by the mental nerve, a branch of the mandibular division of the trigeminal nerve (cranial nerve V3). Similar to the upper lip, it transmits sensations of touch, temperature, and pain.
Motor Innervation: Moving the Lip
The buccal branch of the facial nerve (cranial nerve VII) is responsible for the motor function of the lips. This nerve controls the muscles that allow for lip movements, such as smiling, frowning, pursing, and speaking. Specifically, it innervates the orbicularis oris muscle and other lip elevators.
The information above summarizes the major nerves responsible for the lip's functionality. Damage to these nerves can lead to a variety of symptoms, including altered sensation or loss of movement in the lips. Conditions such as Bell's palsy (affecting facial nerve) or trigeminal neuralgia (affecting trigeminal nerve) can illustrate this.
