Lateral cricoarytenoid muscle
Lateral cricoarytenoid is a bilateral muscle attaching between the cricoid and arytenoid cartilages of the larynx. It is one of the intrinsic muscles of the larynx along with the oblique arytenoid, aryepiglotticus, transverse arytenoid, posterior cricoarytenoid, cricothyroid, thyroaritenoid, vocalis and thyroepiglottic muscles.
The intrinsic muscles of the larynx are involved in the production of sound. They do this by moving the various parts of larynx; changing the state of the vocal folds (i.e. tension and length) and opening or closing the rima glottidis. Specifically, the main function of the lateral cricoarytenoid muscle is to aid sound production by adducting the vocal folds.
This article will discuss the anatomy and function of lateral cricoarytenoid muscle.
|Origin||Arch of cricoid cartilage|
|Insertion||Muscular process of arytenoid cartilage|
|Action||Adducts and shortens vocal folds|
|Innervation||Inferior laryngeal nerve (of recurrent laryngeal nerve (CN X))|
|Blood supply||Laryngeal branches of superior and inferior thyroid arteries|
Origin and insertion
The small, somewhat oblong shaped lateral cricoarytenoid muscle originates from the upper margin of the arch of cricoid cartilage. It courses posteromedially and inserts into the anterior surface of muscular process of arytenoid cartilage.
The muscle is located laterally to vocal folds. Its insertion is closely related to transverse arytenoid and posterior cricoarytenoid muscles as they all insert to the muscular process of arytenoid cartilage.
Lateral cricoarytenoid is innervated by the vagus nerve (CN X) through the anterior branches of recurrent laryngeal nerve.
This muscle is vascularized by the laryngeal branches of superior and inferior thyroid arteries.
The intrinsic laryngeal muscles, of which the lateral cricoarytenoid is a part, are all involved in the production of sound (phonation). They do so by moving the various parts of larynx; changing the state of the vocal folds (i.e. tension and length) and opening or closing the rima glottidis.
When the lateral cricoarytenoid muscles contract, they rotate the arytenoid cartilages and thus medially swing the vocal process onto which the vocal ligaments are attached. This brings the tips of the vocal processes together; resulting in adduction of the vocal folds and closure of the anterior part of the rima glottidis.
Relating this to speech; lateral cricoarytenoid rotates the arytenoid cartilages while the transverse and oblique arytenoid muscles simultaneously pull the arytenoid cartilages toward each other (closing the posterior part of the rima glottidis; adductive tension). Together these actions adducts the vocal folds, closes the rima glottidis and narrows the laryngeal inlet. When expired air passes through the closed rima glottidis, it is directed towards the adducted vocal folds, causing the folds to vibrate and produce voiced sounds.
Acting on its own, lateral cricoarytenoid is unable to fully close the rima glottidis. Some air bypasses the vocal folds and therefore is not able to cause their full resonance. This produces whispering.
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