Alar part of nasalis muscle

The alar part of nasalis muscle, sometimes referred to as the dilator naris, forms the inferior division of the nasalis muscle. It acts to dilate or flare the nostrils, counterbalancing the compressive effect of the transverse part.

Anatomical Details

1. Origin

From the maxilla, just above the lateral incisor region.

2. Course

Fibres pass superiorly and medially toward the lower margin of the nose.

3. Insertion

Into the greater alar cartilage of the nose.

Innervation

Facial nerve (cranial nerve VII) — via its buccal branch.

Blood Supply

Facial artery, a branch of the external carotid artery.

Action

The alar part of nasalis muscle draws the ala of the nose downward and laterally, widening (dilating) the nostrils. The alar part acts in opposition to the transverse (compressor) part of the nasalis. Their coordinated activity finely adjusts the size of the nasal aperture during breathing and emotional expression.