The nasalis has two functionally opposite parts: the transverse compressor narrows the nasal aperture during forced exhalation and expressive nose wrinkling, while the alar dilator opens the nostril during forced nasal inspiration. Together they provide dynamic control of nasal airflow. Nostril flaring from the alar part is part of the anger and excitement expression repertoire, reflecting the evolutionary role of nasal dilation in preparing for physical exertion.
| Origin | Maxilla lateral to the nasal notch |
|---|---|
| Insertion | Transverse part: continues over the dorsum to the opposite side as the nasal aponeurosis. Alar part: inserts into the alar cartilage |
| Nerve Supply | Buccal branch of the facial nerve (CN VII) |
| Blood Supply | Angular and lateral nasal arteries |
| Actions | Transverse (compressor) part: compresses the nasal aperture; Alar (dilator) part: dilates the nostril |
|---|
During peak athletic effort the nasalis alar part dilates the nostrils to reduce inspiratory resistance, contributing to the characteristic nostril flaring visible in sprinters at full effort and in individuals with nasal valve collapse and chronic obstruction.
Nasal valve collapse, where the lateral nasal wall including the alar cartilage collapses during inspiration, is partly addressed by training the nasalis to actively dilate the nostril — the basis of nasal dilator strips like Breathe Right. Septoplasty and functional rhinoplasty address the structural components while the nasalis remains the dynamic component.
The transverse nasalis is palpable over the nasal bridge during deliberate nose wrinkling, and the alar part can be felt contracting at the nostril rim during forced deep nasal inhalation.
Alar cartilage and nasalis weakness producing inspiratory nostril collapse and nasal obstruction, managed with nasal dilator strips, functional rhinoplasty, or alar batten graft reconstruction.
