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Zygomaticus major muscle

The Zygomaticus major muscle is a prominent facial muscle responsible for elevating the angle of the mouth, playing a key role in smiling and expressions of joy. Located in the cheek region, it runs diagonally from the cheekbone to the corner of the mouth and is essential for facial aesthetics and emotional expression. Its anatomical significance, functional dynamics, and clinical appearance on imaging modalities like MRI and CT make it a critical focus in both medical and dental fields.

Anatomy of Zygomaticus Major Muscle

  • Origin:

    • Lateral aspect of the zygomatic bone (cheekbone), just anterior to the zygomaticotemporal suture.

  • Insertion:

    • Skin at the angle of the mouth (modiolus) and blends with fibers of the orbicularis oris and other surrounding muscles.

  • Function:

    • Elevates and draws the angle of the mouth laterally and upward.

    • Produces expressions such as smiling, laughing, and grinning.

    • Assists in exposing the teeth during smiling.

  • Nerve Supply:

    • Zygomatic and buccal branches of the facial nerve (cranial nerve VII).

  • Artery Supply:

    • Facial artery (a branch of the external carotid artery), specifically the superior labial and transverse facial arteries.

  • Vein Supply:

    • Facial vein and its branches, draining into the internal jugular vein.

Imaging Appearance

  • MRI Appearance:

    • T1-Weighted Images:

      • Muscle appears as an intermediate-to-low signal intensity structure compared to surrounding fat.

    • T2-Weighted Images:

      • Normal muscle demonstrates relatively low signal intensity, but increased signal may indicate edema or pathology.

    • STIR (Short Tau Inversion Recovery):

      • Muscle signal is suppressed; pathology such as edema or inflammation appears as high signal (bright) against the suppressed background.

  • CT Appearance:

    • The Zygomaticus major muscle appears as a soft tissue density band extending from the zygomatic bone to the modiolus of the mouth.

    • Best visualized in thin-slice axial and coronal reconstructions; muscle itself is isodense to other facial muscles, distinguishable from surrounding fat.

MRI images

Zygomaticus major muscle mri axial image -img-00000-00000

MRI images

Zygomaticus major muscle

CT images

Zygomaticus major muscle CT axial image-img-00000-00000