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Nasalis muscle

The nasalis muscle is a paired facial muscle located over the nasal bridge, primarily involved in movements of the nasal aperture. It is one of the key muscles of facial expression, contributing to actions such as flaring and compressing the nostrils. Anatomically, it is a thin, broad muscle, forming the largest component of the nasal group of facial muscles. This muscle plays an important role in both functional (breathing) and nonverbal communicative (facial expressions) aspects of nasal movement.

Synonyms

  • Musculus nasalis

  • Nasal muscle

  • Compressor naris (for its transverse part)

  • Dilator naris (for its alar part)

Function

  • Compresses the nasal aperture (transverse part)

  • Flares/dilates the nostrils (alar part)

  • Assists in facial expressions such as sneering or expressing distaste

  • Modifies airflow through the nasal passages

Origin

  • Transverse part: Maxilla, just lateral to the nose (superior aspect of the canine ridge)

  • Alar part: Maxilla, over the lateral incisor region

Insertion

  • Transverse part: Aponeurosis across the dorsum of the nose, merging with the opposite side

  • Alar part: Greater alar cartilage of the nose, and skin at the nostril margin

Nerve Supply

  • Facial nerve (Cranial Nerve VII), specifically via the buccal branch

Artery Supply

  • Superior labial branch of the facial artery

  • Lateral nasal branch of the facial artery

Vein Supply

  • Facial vein (draining via the angular and lateral nasal veins)

MRI Appearance

  • T1-weighted imaging:

    • Isointense to other skeletal muscles; appears as a thin, low-to-intermediate signal band over the nasal bridge

  • T2-weighted imaging:

    • 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 thin, soft tissue density band overlying the nasal bones and cartilages

  • Difficult to differentiate in the absence of contrast or pathology; best visualized in high-resolution facial bone protocols

MRI images

Nasalis muscle mri axial image -img-00000-00000