The Nasalis is a crucial muscle of the face, specifically located on the nose, playing a key role in various nasal movements and facial expressions. It is often described as a sphincter-like muscle due to its action on the nasal cartilages.
The Nasalis Muscle: An Overview
The Nasalis muscle is an intrinsic muscle of the nose, meaning it originates and inserts entirely within the nasal region. Its primary function involves controlling the size of the nostrils, which impacts both breathing and non-verbal communication. It is one of several muscles of facial expression and is particularly active when expressing emotions or during strenuous physical activity.
Anatomy and Structure
The Nasalis muscle is distinctly divided into two main parts, each contributing to different actions on the nose:
The Transverse Part (Compressor Nasi)
This is the upper, broader part of the Nasalis muscle. It originates from the maxilla (the upper jaw bone) lateral to the incisive fossa and inserts into an aponeurosis (a broad tendon) that crosses the bridge of the nose, merging with the aponeurosis from the opposite side.
- Primary Action: The transverse part is responsible for compressing the nasal cartilages. This action narrows the nasal aperture, effectively reducing the size of the nostrils. It is often involved in expressions of disgust or when trying to block unpleasant odors.
The Alar Part (Dilator Nasi)
The alar part is the lower, more medial portion of the Nasalis muscle. It originates from the maxilla above the lateral incisor and inserts into the alar cartilage of the nose.
- Primary Action: The alar part's main role is to flare the nostrils, or dilate the nasal opening. This action is commonly observed during deep breathing, strenuous exercise to maximize airflow, or in expressions of anger, fear, or surprise.
To summarize the distinct roles of its parts:
| Part | Primary Action | Effect on Nostrils |
|---|---|---|
| Transverse | Compresses nasal cartilages | Narrows (constricts) |
| Alar | Flares (dilates) nostrils | Widens (expands) |
Functions and Importance
The Nasalis muscle's actions are vital for several physiological and expressive functions:
- Airflow Regulation: By both compressing and dilating the nostrils, the Nasalis helps control the amount of air entering the respiratory system, adapting to the body's needs during rest or exertion.
- Facial Expressions: It contributes significantly to a range of non-verbal cues. For example, the transverse part contributes to a "wrinkling" of the nose in disgust, while the alar part helps convey intensity in emotions like anger.
- Olfaction: By subtly adjusting nasal airflow, it can assist in the process of smelling.
Clinical Significance
Understanding the Nasalis muscle is important in several medical and aesthetic contexts:
- Facial Nerve Assessment: As with other facial muscles, the function of the Nasalis can be used to assess the integrity of the facial nerve (cranial nerve VII), which innervates it. Damage to this nerve can lead to an inability to move the nose.
- Rhinoplasty: In cosmetic nasal surgery (rhinoplasty), surgeons consider the Nasalis muscle's impact on nasal shape and function to achieve desired aesthetic and functional outcomes.
Innervation
Like most muscles of facial expression, the Nasalis muscle receives its motor innervation from branches of the facial nerve (cranial nerve VII). Specifically, the buccal branch of the facial nerve supplies the Nasalis, enabling its complex movements.
