Mentalis muscle: origin, insertion, action and innervation

The mentalis is a small, paired muscle of facial expression in the chin, running from the front of the mandible to the skin of the chin. It lifts and wrinkles the chin and pushes the lower lip up and out, as in a pout, and it is supplied by the marginal mandibular branch of the facial nerve.

Where it is

The two mentalis muscles sit side by side on the front of the chin, one on each side of the midline, just below the roots of the lower incisor teeth. Each is a short, cone-shaped bundle.

The mentalis lies deep and close to the midline. Its neighbors are:

• the depressor labii inferioris, just lateral to it, which pulls the lower lip down;
• the orbicularis oris, the ring of muscle in the lips, just above it.

Its name comes from the Latin mentum, "chin". The same root gives the mental foramen and the mental protuberance of the mandible.

Origin and insertion

• Origin: the incisive fossa of the mandible, a shallow hollow in the bone below the lower incisors.
• Insertion: the skin of the chin.

Unlike most muscles, which pull one bone toward another, the mentalis runs from bone to skin. Its fibers run downward and forward from the jaw to the soft tissue of the chin, so when they shorten they lift the skin of the chin upward.

What it does

1. Lifting and wrinkling the chin: the mentalis raises the soft tissue of the chin and creases the skin, giving it a dimpled, puckered look.
2. Pushing the lower lip up and out: as the chin skin rises, it pushes the lower lip upward and forward. This is the pout of doubt or displeasure, and the movement of a child about to cry.
3. Helping with drinking: protruding the lower lip helps hold the rim of a cup and keeps liquid in the mouth.

Its neighbors below the mouth, the depressor labii inferioris and the depressor anguli oris, both pull downward; the mentalis pushes the lower lip up.

Innervation and blood supply

The mentalis is supplied by the marginal mandibular branch of the facial nerve (cranial nerve VII). This branch runs forward along the lower border of the mandible and supplies the muscles of the lower lip and chin. Like all muscles of facial expression, the mentalis gets its motor supply from the facial nerve, not from the trigeminal nerve that supplies the chewing muscles such as the masseter.

Its blood comes from the inferior labial artery, a branch of the facial artery, and from the mental artery, which leaves the mandible through the mental foramen.

How to remember it

• Mentum = chin: the mentalis is the chin muscle.
• The odd one out: among the lower lip muscles, the depressors pull down; the mentalis is the only one that pushes up.
• The pout test: push your lower lip out as if you were sulking. The bumpy chin you see in the mirror is the mentalis at work.
• Chin skin, not lip: the two depressors end in the lower lip or its corner; the mentalis ends in the skin of the chin.

Compare it with the other lip muscles on the muscles of the face page, then test yourself in the head quiz.

Frequently asked questions

What does the mentalis muscle do?

It elevates and wrinkles the skin of the chin and pushes the lower lip up and forward, as when you pout.

Which nerve supplies the mentalis?

The marginal mandibular branch of the facial nerve (VII).

Where does the mentalis attach?

It arises from the incisive fossa of the mandible, below the lower incisors, and inserts into the skin of the chin.

Why does my chin dimple when I pout?

Because the mentalis pulls the skin of the chin upward and crumples it as it lifts the lower lip.

Sources

• OpenStax, Anatomy and Physiology 2e, 11.3 Axial muscles of the head, neck and back
• OpenStax, Anatomy and Physiology 2e, 13.4 The peripheral nervous system
• Z-Anatomy, the libre 3D atlas of anatomy