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Mentalis muscle

The mentalis muscle is a small, paired facial muscle located in the chin region. It plays a crucial role in the movement and expression of the lower lip and chin. It is particularly important for actions such as pouting and the elevation of the lower lip. Clinically, the mentalis is involved in both voluntary and involuntary facial expressions, and its anatomy is essential for procedures in plastic and reconstructive surgery.

Synonyms:

  • Musculus mentalis

  • Chin muscle

Function:

  • Elevates and protrudes the lower lip

  • Wrinkles the skin of the chin

  • Assists in expressing doubt, disdain, or pouting

  • Important for functions like speech, eating, and facial expressions

Origin:

  • Incisive fossa of the mandible, below the lower incisors

Insertion:

  • Skin of the chin (specifically, the integument of the chin and the skin over the mental protuberance)

Nerve Supply:

  • Mandibular branch of the facial nerve (cranial nerve VII), specifically via the marginal mandibular branch

Artery Supply:

  • Inferior labial branch of the facial artery

  • Mental branch of the inferior alveolar artery

Vein Supply:

  • Accompanying veins follow the arteries, mainly draining into the inferior labial vein and mental vein, which ultimately drain into the facial vein

MRI Appearance:

  • T1-weighted images: Appears as an intermediate to low signal intensity structure, distinguishing muscle from surrounding fat and connective tissue.
  • T2-weighted images: Normal muscle demonstrates relatively low signal intensity, but increased signal may indicate edema or pathology.
  • STIR (Short Tau Inversion Recovery): Muscle shows low signal intensity in healthy tissue; hyperintensity is seen if there is edema, inflammation, or acute injury.

 

CT Appearance:

  • Appears as a soft tissue structure in the chin region

  • Borders are well-defined, especially with high-resolution facial CT

MRI images

Mentalis muscle MRI axial image