Mentalis

The mentalis muscle is a paired central muscle of the lower lip, situated at the tip of the chin. It originates from the mentum of the mandible, and inserts into the soft tissue of the chin. It is sometimes referred to as the "pouting muscle" due to it raising the lower lip and causing chin wrinkles.

Structure

The mentalis muscle originates from the mental protuberance of the mandible near the midline. It inserts into the soft tissue and skin of the chin.

Function

The mentalis muscle causes a weak upward-inward movement of the soft tissue complex of the chin. This raises the central portion of the lower lip. In the setting of lip incompetence, the contraction of the mentalis muscle can bring temporary but strained oral competence.
In conjunction with the orbicularis [oris muscle], the mentalis muscle allows the lips to "pout". Externally, contraction of the mentalis muscle causes wrinkling and dimpling of the skin on the chin, as used in expressions of doubt or displeasure.

Clinical significance

The mentalis muscle can be easily assessed using ultrasound.

Geniospasm

is a genetic movement disorder of the mentalis muscle. It involves repetitive contraction of the muscle, with episodes lasting between seconds and hours. Certain medications may be used to treat it, such as haloperidol and benzodiazepines. Injection of botulinum toxin may be more effective.

Cosmetics

The mentalis muscle may be partially paralysed using botulinum toxin to reduce wrinkling of the skin of the chin. This may be done for cosmetic purposes.