Depressor Septi Nasi

Facial Expression · Head & Neck

Depressor Septi Nasi belongs to the Facial Expression group of the Head & Neck. Originating at Incisive fossa of the maxilla (above the central incisor), it inserts at Mobile part of the nasal septum and posterior aspect of the ala. When it contracts, it depresses the nasal septum and constricts the nostril. Its nerve supply is the Buccal branch of facial nerve (CN VII).

Origin, Insertion, Action & Nerve

Origin

Incisive fossa of the maxilla (above the central incisor)

Insertion

Mobile part of the nasal septum and posterior aspect of the ala

Action

Depresses the nasal septum and constricts the nostril

Nerve

Buccal branch of facial nerve (CN VII)

Attachments explained

The Depressor Septi Nasi 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

Incisive fossa of the maxilla (above the central incisor)

Insertion

Mobile part of the nasal septum and posterior aspect of the ala

Action & function

When the Depressor Septi Nasi contracts, it produces the following movement: Depresses the nasal septum and constricts the nostril.

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 Depressor Septi Nasi 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 Depressor Septi Nasi, impairing the movements it normally produces (depresses the nasal septum and constricts the nostril). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Depressor Septi Nasi (the OIANS method)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Depressor Septi Nasi, 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 Depressor Septi Nasi 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.