Nasalis muscle

At a glance

English

Nasalis muscle

Latin (TA2)

Musculus nasalis

System

Muscle

Region

Head

Side

Paired, left and right

About the nasalis muscle

The nasalis is a thin muscle of facial expression spread over the lower, cartilaginous half of the nose. It is described in two parts that work in opposite ways: a transverse part across the bridge that narrows the nostrils, and an alar part at the wing that widens them. Between them they adjust the size of the nasal openings, and some people can use the muscle to close the nostrils when swimming under water.

Both parts take origin from the maxilla. The transverse part, sometimes called the compressor naris, arises lateral to and a little above the incisive fossa, over the canine and lateral incisor region. Its fibres pass up and towards the midline and spread into a thin aponeurosis over the bridge of the nose, which joins that of the other side and the aponeurosis of the procerus. The alar part, or dilator naris, arises a little lower and more medially, above the lateral incisor root, and ends in the greater alar cartilage and the skin of the nostril wing. Its innermost fibres blend with depressor septi nasi, and some anatomists count them as part of that muscle.

The transverse part compresses the nasal cartilages and narrows, or even closes, the nostril. The alar part pulls the wing of the nose down and outwards, flaring the opening, as seen in hard breathing or anger. As with every muscle of expression, its nerve is the facial nerve, through its buccal and zygomatic branches, and its blood comes from the superior labial and lateral nasal branches of the facial artery.

Because it lies just under the skin, flaring or wrinkling the nose is an easy bedside test of the facial nerve. The muscle is also important in cleft lip, where it fails to form or attach normally; during repair the surgeon finds where the transverse part begins and stitches it to the nasal septum, and may move its maxillary origin to improve symmetry.

Attachments, action and supply

Origin

Maxilla: transverse part lateral to and a little above the incisive fossa; alar part above the lateral incisor root.

Insertion

Transverse part into an aponeurosis over the nasal bridge joining its fellow and the procerus; alar part into the greater alar cartilage.

Action

Transverse part compresses the nasal aperture; alar part draws the ala down and out, flaring the nostril.

Nerve supply

Buccal and zygomatic branches of the facial nerve (cranial nerve VII).

Blood supply

Superior labial and lateral nasal branches of the facial artery.