The mentalis muscle is a paired muscle located at the tip of the chin. It acts as the primary muscle of the lower lip.
The mentalis originates from the mandible (lower jaw) and runs vertically from below the lower lip to the lower part of the chin. This muscle provides stability to the lower lip to allow it to pout. It causes protrusion of the lower lip and elevates the skin of the chin.
As the lower lip is raised, it results in elevation and wrinkling of the chin's skin. The mentalis is so named because of its association with emotional and thoughtful facial expressions.
The zygomatic facial nerve supplies this muscle. The facial artery is the source of its blood supply.
The mentalis is generally not associated with any facial problems. In rare cases it may result in medical disorders.
One of the movement disorders caused by the mentalis muscle is referred to as geniospasm, which causes uncontrollable tremors of the chin and lower lip.
This is a harmless condition that usually begins in childhood and may occur due to genetic factors. Geniospasm can be a socially problematic condition and may require medical care.