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Topic

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Depressor anguli oris muscle

The Depressor Anguli Oris muscle is a paired, superficial muscle located in the lower part of the face. It plays a critical role in facial expression, specifically in depressing the corners of the mouth, as seen during expressions of sadness or frowning. This muscle is clinically significant due to its involvement in facial nerve disorders and cosmetic procedures.

Synonyms

  • DAO muscle

  • Triangularis muscle

  • Depressor of the angle of the mouth

Function

  • Depresses the angle of the mouth (downward and laterally), contributing to frowning or sad facial expressions

  • Assists in the movement of the lower lip

Nerve Supply

  • Facial nerve (Cranial Nerve VII), specifically the marginal mandibular branch

Artery Supply

  • Facial artery (main supply)

  • Inferior labial branch of the facial artery

  • Contributions from the mental branch of the inferior alveolar artery

Vein Supply

  • Facial vein

  • Inferior labial vein

MRI Appearance

  • T1-weighted images: Appears as intermediate to low signal intensity relative to subcutaneous fat

  • T2-weighted images: Shows  intermediate to low signal intensity.

  • STIR (Short Tau Inversion Recovery): The muscle appears with suppressed fat signal and mild hyperintensity if there is edema or pathology

CT Appearance

  • Appears as a soft tissue structure of similar density to other facial muscles

  • Seen as a thin, triangular muscle at the lower corner of the mouth, superficial to the mandible

MRI images

Depressor anguli oris muscle mri axial image

MRI images

Depressor anguli oris muscle mri axial image1