Nasalis (Alar Part)
Facial Expression · Head & Neck
The alar part of nasalis, sometimes called the dilator naris, is the portion of the nasalis muscle that widens the nostril. It arises from the maxilla over the alveolar eminence of the lateral incisor and inserts into the skin and alar cartilage at the margin of the nostril. On contraction it draws the ala downward and laterally, dilating the nostril and enlarging the nasal aperture, an action recruited during deep or forced inspiration and flaring of the nostrils. Like the rest of the nasalis and the other muscles of facial expression, it is supplied by the facial nerve (CN VII) through its buccal branch. It is the functional antagonist of the transverse (compressor) part of nasalis.
Origin, Insertion, Action & Nerve
Origin
Maxilla, over the alveolar eminence of the lateral incisor
Insertion
Skin and alar cartilage at the margin of the nostril
Action
Dilates the nostril (flares the nasal aperture)
Nerve
Buccal branch of facial nerve (CN VII)
Attachments explained
The Nasalis (Alar Part) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Maxilla, over the alveolar eminence of the lateral incisor
Insertion
Skin and alar cartilage at the margin of the nostril
Action & function
When the Nasalis (Alar Part) contracts, it produces the following movement: Dilates the nostril (flares the nasal aperture).
As part of the Facial Expression group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Nasalis (Alar Part) receives its nerve supply from the Buccal branch of facial nerve (CN VII).
Because a muscle can only contract when its nerve is intact, injury to the Buccal branch of facial nerve can weaken or paralyse the Nasalis (Alar Part), impairing the movements it normally produces (dilates the nostril (flares the nasal aperture)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Nasalis (Alar Part) (the OIANS method)
Use the alternative name dilator naris to lock in the action: this part of nasalis dilates, or opens, the nostril. Because it attaches directly to the alar cartilage at the nostril margin, its pull flares the ala outward; watching the nostrils widen during a deep breath demonstrates it clearly. Fix its origin as the maxilla over the lateral incisor, one tooth medial to the transverse part over the canine.
Study it as the antagonist within nasalis: the alar part opens the nostril, the transverse part closes it, and both share the facial nerve (CN VII) via the buccal branch. Learning the two parts as a paired dilator and compressor with a common nerve turns four separate facts into a single, memorable relationship.
Frequently asked questions
Where is the Nasalis (Alar Part) located?
The Nasalis (Alar Part) is a muscle of the Facial Expression group, located in the Head & Neck.
What is the origin of the Nasalis (Alar Part)?
Maxilla, over the alveolar eminence of the lateral incisor
What is the insertion of the Nasalis (Alar Part)?
Skin and alar cartilage at the margin of the nostril
What movements does the Nasalis (Alar Part) produce?
Dilates the nostril (flares the nasal aperture)
What nerve supplies the Nasalis (Alar Part)?
Buccal branch of facial nerve (CN VII)
Is the Nasalis (Alar Part) free to study in OIANS?
The Nasalis (Alar Part) is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Head & Neck is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
Study the Nasalis (Alar Part)
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