Nasalis (Alar Part)

Facial Expression · Head & Neck

Located in the Facial Expression of the Head & Neck, the Nasalis (Alar Part) is a key muscle for anatomy study. Its origin is Maxilla, over the alveolar eminence of the lateral incisor, and it inserts onto Skin and alar cartilage at the margin of the nostril. Functionally, it dilates the nostril (flares the nasal aperture). Innervation is provided by the Buccal branch of facial nerve (CN VII).

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)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Nasalis (Alar Part), work through them in order: picture its origin, trace the muscle to its insertion, reason out the action that shortening between those two points must create, then add the nerve that drives it.

Most students remember the Nasalis (Alar Part) fastest by linking its action back to its attachments rather than memorising each fact in isolation. Once the origin and insertion make sense, the action usually follows logically.