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Depressor septi nasi muscle

The depressor septi nasi muscle is a small paired muscle of facial expression located in the lower part of the nose. It plays an essential role in nasal movements, particularly influencing the nasal septum and nostrils during facial expressions and respiration. The muscle extends from the maxilla to the nasal septum and the lower part of the nostrils. Although not always prominently visible, it contributes to the downward movement of the nasal septum and nostril base during smiling or speaking.

Synonyms

  • Depressor septi

  • Musculus depressor septi nasi

  • Nasal septum depressor muscle

Function

  • Depresses the nasal septum

  • Draws the ala of the nose downward, narrowing the nostrils

  • Contributes to facial expressions, especially during smiling and speaking

  • Aids in the regulation of nostril width during respiration

Nerve Supply

  • Innervated by the buccal branch of the facial nerve (cranial nerve VII)

Artery Supply

  • Supplied primarily by branches of the superior labial artery (a branch of the facial artery)

Vein Supply

  • Drained via the facial vein through tributaries corresponding to the superior labial vein

MRI Appearance

  • T1-weighted images: Appears as a thin, low-to-intermediate signal intensity structure, similar to other skeletal muscles

  • T2-weighted images: Demonstrates slightly higher signal intensity compared to T1, but remains relatively low, distinguishing muscle from surrounding fat and subcutaneous tissues

  • STIR (Short Tau Inversion Recovery): Shows low signal intensity, unless there is pathology or edema, in which case the signal increases

CT Appearance

  • Appears as a thin, soft tissue density structure inferior to the nasal septum, often challenging to visualize distinctly due to its small size and proximity to surrounding soft tissues

  • Best visualized in high-resolution, thin-slice facial CT scans

MRI images

Depressor septi nasi muscle mri axial image