Depressor septi nasi
The depressor septi nasi is a small muscle under the upper lip that pulls the nasal septum and nostril margins down, narrowing the nostrils.
At a glance
- English
- Depressor septi nasi
- Latin (TA2)
- Depressor septi nasi
- System
- Muscle
- Region
- Head
- Side
- Paired, left and right
About the depressor septi nasi
The depressor septi nasi is one of the small muscles of the nose. It lies in the upper lip, between the lining of the mouth and the main muscle layer of the lip, so it sits deep and close to the midline under the nose. Paired, one on each side of the septum, it is the main downward puller of the tip of the nose, and its action can be seen in some people as a dip of the nasal tip and a shortening of the upper lip when they smile.
It arises from the maxilla's incisive fossa, the shallow hollow above the roots of the central and lateral incisors, and it may also take fibres from the deep layer of orbicularis oris. Its fibres run upwards to the mobile part of the nasal septum and to the hind edge of nasalis where it grips the nostril. Some anatomists regard it as a slip of nasalis, the alar portion, with which it merges.
When it contracts it draws the septum and the wings of the nose downwards, which narrows the nostrils. In this it opposes the dilator muscles of the nose and works in the same direction as the alar portion of nasalis, together helping to constrict the opening, for example to keep out water. As a muscle of expression it is driven by the facial nerve, through its buccal branches, and it receives blood from the superior labial branch of the facial artery.
The muscle matters in nasal surgery. An overactive depressor septi nasi can cause the tip to droop when smiling and deepen the crease of the upper lip. During rhinoplasty the surgeon may therefore release, divide or reposition its upper attachment to keep the tip in a stable position after the operation; several techniques give similar results. It can also be weakened with botulinum toxin for the same effect.
Attachments, action and supply
- Origin
- The maxilla's incisive fossa, with some fibres from orbicularis oris.
- Insertion
- Mobile part of the nasal septum and the hind edge of the alar portion of nasalis.
- Action
- Pulls the nasal septum and alae downwards, narrowing the nostrils.
- Nerve supply
- Facial nerve (VII), buccal branches.
- Blood supply
- Superior labial branch of the facial artery.
Anthromica
See the depressor septi nasi where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
