Depressor septi nasi: origin, insertion, action and innervation

The depressor septi nasi is a tiny muscle under the upper lip that pulls the nasal septum and the tip of the nose downward. It runs from the maxilla, just above the front teeth, to the columella between the nostrils, and it is supplied by the buccal branch of the facial nerve (CN VII).

Where it is

The muscle sits in the upper lip, in the midline region just below the nose. It lies deep to the orbicularis oris and close to the mucosa of the mouth, so it cannot be seen from the surface. Its fibers run almost vertically, from the gum line above the central incisors up to the base of the nose.

It is one of the small muscles of the nose, with the nasalis, the procerus and the levator labii superioris alaeque nasi. Some anatomists treat it as a slip of the nasalis or of the orbicularis oris, because its fibers mix with both.

The name is plain Latin: depressor (it lowers), septi (of the septum), nasi (of the nose).

Origin and insertion

• Origin: the incisive fossa of the maxilla, a shallow hollow on the front of the upper jaw above the central incisor tooth. The maxilla is one of the facial bones described on the skull page.
• Insertion: the mobile part of the nasal septum, the columella, which is the strip of skin and cartilage between the nostrils, and the back of the alar cartilage, the cartilage of the wing of the nose.

What it does

The depressor septi nasi draws the nasal septum and the tip of the nose downward, pulling on the columella and the back of the ala.

Its action is small, and in many people it is hard to see. In others it shows clearly when they smile: the tip of the nose dips and the upper lip shortens at the same moment, because the muscle links the lip and the nose. Watch the tip of your own nose in a mirror while you smile broadly to see whether yours is one that shows.

Its opposite is the levator labii superioris alaeque nasi, which lifts the wing of the nose and flares the nostril. The alar part of the nasalis also widens the nostril, while its transverse part compresses the bridge of the nose.

Innervation and blood supply

The muscle is supplied by the buccal branch of the facial nerve. The buccal branches cross the face horizontally from the front of the parotid gland and supply the muscles of the upper lip, the nose and the cheek, including the buccinator.

Its blood comes from the superior labial artery, a branch of the facial artery that runs along the upper lip just deep to the orbicularis oris and gives a small branch to the nasal septum.

How to remember it

• Septum down: the name gives both the target and the direction.
• Teeth to tip: it starts above the front teeth and ends at the tip of the nose, a short vertical strap.
• Smile dip: when someone's nose tip drops as they smile, think of this muscle.
• Two nose openers, one nose lowerer: the levator labii superioris alaeque nasi and the alar part of the nasalis flare the nostrils; the depressor septi nasi pulls the tip down.

Place it among the other muscles around the nose and mouth on the muscles of the face page, then test yourself in the head quiz.

Frequently asked questions

What does the depressor septi nasi do?

It pulls the nasal septum and the tip of the nose downward.

Which nerve supplies the depressor septi nasi?

The buccal branch of the facial nerve (CN VII).

Where does the depressor septi nasi attach?

From the incisive fossa of the maxilla, above the central incisor, to the columella and the back of the alar cartilage.

Why does my nose tip move down when I smile?

In some people the depressor septi nasi contracts with the lip muscles during a smile and pulls the nasal tip down.

Sources

• OpenStax, Anatomy and Physiology 2e, 11.3 Axial muscles of the head, neck and back
• OpenStax, Anatomy and Physiology 2e, 7.2 The skull
• Z-Anatomy, the libre 3D atlas of anatomy