Laryngeal muscles

The muscles of the larynx are divided by their functional features into muscles that stretch the vocal cords, expanders and constrictors of the glottis. All muscles of the larynx, except for the transverse arytenoid, are paired.

Two muscles tense (stretch) the vocal cords (ligg.vocalia): the cricothyroid and vocal muscles.

Muscles of the larynx

Muscles	Start	Attachment	Function	Innervation
Muscles that tense (stretch) the vocal cords
Cricothyroid muscle	Anterior surface of the cricoid arch	Lower edge of the plate, lower horn of the thyroid cartilage	Tilts the thyroid cartilage forward	Superior laryngeal nerve
Vocal muscle	Angle of the thyroid cartilage	Vocal process of the arytenoid cartilage, vocal cord	Pulls the vocal cord forward and backward (strains it)	Inferior laryngeal nerve
Muscles that dilate the glottis
Posterior cricoarytenoid muscle	Posterior surface of the cricoid cartilage plate	Muscular process of the arytenoid cartilage	Pulls the muscular process of the arytenoid cartilage backwards, while the vocal process rotates laterally	Same
Muscles that constrict the glottis
Lateral cricoarytenoid muscle	Upper edge of the cricoid arch	Same	Pulls the muscular process of the arytenoid cartilage forward, while the vocal process rotates medially	» »
Oblique arytenoid muscle	Muscular process of the arytenoid cartilage	Apex of the opposite arytenoid cartilage	Brings the right and left arytenoid cartilages closer to each other	Inferior laryngeal nerve
Aryepogarytenoid muscle	Continuation of the previous muscle	Edge of the epigortanus	Pulls the epiglottis backwards, closing the entrance to the larynx	Same
Transverse arytenoid muscle (unpaired)	Lateral margin of the arytenoid cartilage	Lateral edge of the arytenoid cartilage of the other side	Brings the right and left arytenoid cartilages closer to each other	» »

The cricothyroid muscle (m.cricothyroideus) originates on the anterior surface of the cricoid arch and is attached to the thyroid cartilage. There are straight and oblique parts of this muscle. The straight part (pars recta) is attached to the lower edge of the thyroid cartilage, the oblique part (pars obliqua) goes upward and laterally and is attached to the base of the inferior horn of the thyroid cartilage of the larynx. Acting on the cricothyroid joints, this paired muscle tilts the thyroid cartilage forward. The distance between the thyroid cartilage and the vocal processes of the arytenoid cartilages increases, the vocal cords become tense. When the thyroid cartilage returns to its original position, the vocal cords relax.

The vocal muscle (m.vocalis), or internal thyroarytenoid muscle (m.thyroarytenoideus internus - BNA), is located in the thickness of the eponymous fold of the larynx. The muscle begins on the lateral surface of the vocal process of the arytenoid cartilage, goes forward and attaches to the internal surface of the angle of the thyroid cartilage. Some of the fibers of this muscle are woven into the vocal cord. The muscle can contract completely or in separate parts, straining the vocal cord as a whole or in any of its sections.

The posterior cricoarytenoid muscle (m.cricoarytenoideus posterior) widens the glottis. It begins on the posterior surface of the cricoid cartilage, goes upward and laterally, and attaches to the muscular process of the arytenoid cartilage. When contracting, the muscle pulls the vocal process back, turning the arytenoid cartilage outward. The vocal process of the arytenoid cartilage moves laterally, and the glottis widens.

The glottis is narrowed by the lateral cricoarytenoid muscle, the thyroarytenoid, transverse and oblique arytenoid muscles.

The lateral cricoarytenoid muscle (m.cricoarytenoideus lateralis) originates on the lateral part of the cricoid arch. It goes upward and backward, attaching to the muscular process of the arytenoid cartilage. When these muscles contract, the muscular process of the arytenoid cartilage moves forward, and the vocal process moves inward. As a result, the vocal fold (especially its anterior part) narrows.

The thyroarytenoid muscle (m.thyroarytenoideus) begins on the inner surface of the thyroid cartilage plate, goes back and slightly upward, and attaches to the muscular process of the arytenoid cartilage. The muscle also pulls the muscular process forward. The vocal processes come closer together, and the glottis narrows.

The transverse arytenoid muscle (m.arytenoideus transversus), located on the posterior surface of both arytenoid cartilages, when contracted brings the arytenoid cartilages together, narrowing the posterior part of the glottis.

The oblique arytenoid muscle (m.arytenoideus obliquus) is paired and runs from the posterior surface of the muscular process of one arytenoid cartilage upward and medially to the lateral edge of the other arytenoid cartilage. The muscle bundles of the right and left oblique arytenoid muscles cross behind the transverse arytenoid muscle and, when contracted, bring the arytenoid cartilages together. Separate bundles of the oblique arytenoid muscles continue into the thickness of the aryepiglottic folds and are attached to the lateral edges of the epiglottis (aryepiglottic muscle, m.aryepiglotticus). When contracted, these bundles narrow the entrance to the larynx. The aryepiglottic muscles tilt the epiglottis backward, closing the entrance to the larynx (during swallowing).

As a result of the action of the muscles on the cartilages and joints of the larynx, the position of the vocal folds changes, the glottis widens or narrows. During conversational speech, the glottis widens to 10-15 mm (from 5 mm during calm breathing). When shouting, singing, the glottis widens as much as possible. The width of the glottis can be seen during laryngoscopy (examination of the walls of the larynx) in the clinic.

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