Nasalis is a paired muscle that covers the dorsum of the nose. It consists of two parts; alar and transverse. The alar part is also called dilator naris posterior, and the transverse part is known also as the compressor naris. Together with procerus, levator labii superioris alaeque nasi and depressor septi muscles, nasalis belongs to the nasal group of facial muscles.
Like all facial muscles, nasalis is derived from the second pharyngeal arch and thus is innervated by the facial nerve (CN VII). This muscle dilates the nostrils, depresses the ala nasi (nostril wings) laterally and wrinkles the nasal skin. These actions enable flaring of nostrils, which occurs during breathing and is emphasized in various emotionally driven situations.
|Alar part: Frontal process of maxilla (superior to lateral incisor)
Transverse part: Maxilla (superolateral to incisive fossa)
|Alar part: Skin of ala;
Transverse part: Merges with counterpart at dorsum of nose
|Alar part: Depresses ala laterally, dilates nostrils
Transverse part: Wrinkles skin of dorsum of nose
|Buccal branch of facial nerve (CN VII)
|Superior labial, septal, and lateral nasal branches of facial artery;
Infraorbital branch of maxillary artery
This article will discuss the anatomy and function of the nasalis muscle.
Origin and insertion
Nasalis muscles are found on each side of the midline, respectively. Each muscle is composed of two parts; lateral or transverse part (compressor naris) and medial or alar part (dilator naris posterior).
The transverse part covers the dorsum of the nose. It originates from the maxilla, attaching superolateral to the incisive fossa. Its fibers then course superomedially, expanding into a thin aponeurosis at the bridge of the nose. Via this aponeurosis, the muscle inserts at the dorsum of the nose by blending with its counterpart from the opposite side.
The alar part comprises the nostrils. It originates from the frontal process of maxilla, just superior to the lateral incisor. After a short superoanterior course, it inserts to the skin of ala, superior to the lateral crus of major alar cartilage. Here, some fibers blend with the transverse part of nasalis.
Nasalis lies superficial to the nasal bone and lateral nasal cartilage, being covered by the nasal skin. The inserting fibers of its transverse part are directly related to, and may partially blend with, the aponeurosis of procerus muscle. The alar part lies lateral to the depressor septi muscle.
A small muscle called dilator nasi anterior, or apicis nasi, attaches to the anterior margin of the alar part of nasalis muscle. Several arteries and nerves course over the superior surface of nasalis including, the facial artery, terminal branches of the infraorbital artery and nerve, and the external nasal artery and nerve.
Nasalis muscle is innervated by the buccal branch of facial nerve (CN VII).
Blood supply to nasalis comes from the superior labial, septal and lateral nasal branches of facial artery, and the infraorbital branch of maxillary artery.
The transverse part of nasalis wrinkles the nasal skin and compresses the nasal aperture, hence its other name compressor naris. The alar part dilates the nostrils as it pulls the ala laterally, thus its name dilator naris posterior.
All these actions of nasalis normally happen prior to each inspirium, in order to prevent the external nasal valve from collapsing. This function of nasalis is even more notable during deep breathing when these movements are more obvious, as well as in affective emotional states such as anger.
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