The mentalis muscle is a paired central

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

of the

lower lip The lips are a horizontal pair of soft appendages attached to the jaws and are the most visible part of the mouth of many animals, including humans. Mammal lips are soft, movable and serve to facilitate the ingestion of food (e.g. sucklin ...

, situated at the tip of the

chin The chin is the forward pointed part of the anterior mandible (List_of_human_anatomical_regions#Regions, mental region) below the lower lip. A fully developed human skull has a chin of between 0.7 cm and 1.1 cm. Evolution The presence of a we ...

. It originates from the mentum of the

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

, and inserts into the

soft tissue Soft tissue connective tissue, connects and surrounds or supports internal organs and bones, and includes muscle, tendons, ligaments, Adipose tissue, fat, fibrous tissue, Lymphatic vessel, lymph and blood vessels, fasciae, and synovial membranes.� ...

of the chin. It is sometimes referred to as the "pouting muscle" (as in duck face) due to it raising the lower lip and causing chin wrinkles.

Structure

The mentalis muscle originates from the mental protuberance of the

near the midline. It inserts into the

and

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

of the

Function

The mentalis muscle causes a weak upward-inward movement of the

complex of the

. This raises the central portion of the

. In the setting of lip incompetence (the upper and lower lips not touching each other at rest), the contraction of the mentalis muscle can bring temporary but strained oral competence. In conjunction with the orbicularis oris muscle (for the upper lip), the mentalis muscle allows the lips to "pout". Externally, contraction of the mentalis muscle causes wrinkling and dimpling of the

on the chin, as used in expressions of doubt or displeasure.

Clinical significance

The mentalis muscle can be easily assessed using

ultrasound Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply ...

Geniospasm

Geniospasm Geniospasm is movement disorder of the mentalis muscle. It is a benign genetic disorder linked to chromosome 9q13-q21 where there are episodic involuntary up and down movements of the chin and lower lip. The movements consist of rapid fluttering o ...

is a genetic

movement disorder Movement disorders are clinical syndromes with either an excess of movement or a paucity of voluntary and involuntary movements, unrelated to weakness or spasticity. Movement disorders present with extrapyramidal symptoms and are caused by basa ...

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 Haloperidol, sold under the brand name Haldol among others, is a typical antipsychotic medication. Haloperidol is used in the treatment of schizophrenia, tics in Tourette syndrome, mania in bipolar disorder, delirium, agitation, acute psychos ...

and

benzodiazepines Benzodiazepines (BZD, BDZ, BZs), colloquially known as "benzos", are a class of central nervous system (CNS) depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed to treat co ...

. Injection of

botulinum toxin Botulinum toxin, or botulinum neurotoxin (commonly called botox), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon en ...

(to temporarily paralyse the muscle) 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.

Additional images

File:Gray176.png, Outer surface of

. Mentalis is indicated by the red circle at left. File:Mentalis animation small.gif, Position of mentalis (red) File:Braus 1921 376.png, Action of the mentalis muscle

References

{{Authority control Muscles of the head and neck