Thyroarytenoid muscle

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Thyroarytenoid muscle
Musculusthyreoarytenoideus.png
Muscles of the larynx, seen from above.
Details
Origin Inner surface of the thyroid cartilage (anterior aspect)
Insertion Anterior surface of arytenoid cartilage
Nerve Recurrent laryngeal branch of the vagus
Actions Helps to reduce tension on the vocal folds during speech to decrease pitch
Identifiers
Latin Musculus thyroarytenoideus
TA A06.2.08.008
FMA 46588
Anatomical terms of muscle

The thyroarytenoid muscle is a broad, thin muscle that forms the body of the vocal fold and that supports the wall of the ventricle and its appendix. It functions to relax the vocal folds.

Contents

Structure

It arises in front from the lower half of the angle of the thyroid cartilage, and from the middle cricothyroid ligament.

Thyroid cartilage

The thyroid cartilage is the largest of the nine cartilages that make up the laryngeal skeleton, the cartilage structure in and around the trachea that contains the larynx. It does not completely encircle the larynx; only the cricoid cartilage does.

Its fibers pass backward and laterally, to be inserted into the base and anterior surface of the arytenoid cartilage.

Arytenoid cartilage

The arytenoid cartilages are a pair of small three-sided pyramids which form part of the larynx, to which the vocal folds are attached. These allow and aid in the vocal cords' movement.

Parts

The lower and deeper fibers of the muscle can be differentiated as a triangular band which is inserted into the vocal process of the arytenoid cartilage, and into the adjacent portion of its anterior surface; it is termed the Vocalis, and lies parallel with the vocal ligament, to which it is adherent.[ citation needed ]

The vocal muscle is the upper portion of the thyroarytenoid muscle which is primarily involved in producing speech.

A considerable number of the fibers of the thyroarytenoid muscle are prolonged into the aryepiglottic fold, where some of them become lost, while others are continued to the margin of the epiglottis. They have received a distinctive name, thyroepiglottic muscle, thyreoepiglotticus or thyroepiglottic, and are sometimes described as a separate muscle.[ citation needed ]

Aryepiglottic fold Folds near the larynx

The Aryepiglottic folds are triangular folds of mucous membrane enclosing ligamentous and muscular fibres. They are located at the entrance of the larynx, extending from the lateral borders of the epiglottis to the arytenoid cartilages, hence the name 'aryepiglottic'. They contain the aryepiglottic muscles and form the upper borders of the quadrangular membrane.

Thyroepiglottic muscle

A considerable number of the fibers of the thyroarytenoid muscle are prolonged into the aryepiglottic fold, where some of them become lost, while others continue to the margin of the epiglottis. They have received a distinctive name, thyroepiglotticus or thyroepiglottic muscle, and are sometimes described as a separate muscle. This muscle's function is to widen the laryngeal inlet.

A few fibers extend along the wall of the ventricle from the lateral wall of the arytenoid cartilage to the side of the epiglottis and constitute the ventricularis muscle.

Function

The thyroarytenoid muscle, consisting of two parts having different attachments and different directions, are rather complicated as regards their action.

Their main use is to draw the arytenoid cartilages forward toward the thyroid, and thus relax and shorten the vocal folds.

But, owing to the connection of the deeper portion with the vocal fold, this part, if acting separately, is supposed to modify its elasticity and tension, while the lateral portion rotates the arytenoid cartilage inward, and thus narrows the rima glottidis by bringing the two vocal folds together.

Additional images

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The larynx, commonly called the voice box, is an organ in the top of the neck of tetrapods involved in breathing, producing sound, and protecting the trachea against food aspiration. The larynx houses the vocal folds, and manipulates pitch and volume, which is essential for phonation. It is situated just below where the tract of the pharynx splits into the trachea and the esophagus. The word larynx comes from a similar Ancient Greek word.

Rima glottidis Organ

The rima glottidis is the opening between the true vocal cords and the arytenoid cartilages of the larynx.

Cricothyroid ligament

The cricothyroid ligament is composed of two parts:

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Laryngeal inlet

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Subclavius muscle

The subclavius is a small triangular muscle, placed between the clavicle and the first rib. Along with the pectoralis major and pectoralis minor muscles, the subclavius muscle makes up the anterior wall of the axilla.

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The arytenoid is a single muscle, filling up the posterior concave surfaces of the arytenoid cartilages.

Cuneiform cartilages

In the human larynx, the cuneiform cartilages are two small, elongated pieces of yellow elastic cartilage, placed one on either side, in the aryepiglottic fold.

Oblique arytenoid

The oblique arytenoid, the more superficial Arytenoid muscle, forms two fasciculi, which pass from the base of one cartilage to the apex of the opposite one, and therefore cross each other like the limbs of the letter X; a few fibers are continued around the lateral margin of the cartilage, and are prolonged into the aryepiglottic fold; they are sometimes described as a separate muscle, the Aryepiglotticus.

Laryngeal vestibule

The portion of the cavity of the larynx above the vocal folds is called the laryngeal vestibule; it is wide and triangular in shape, its base or anterior wall presenting, however, about its center the backward projection of the tubercle of the epiglottis. It contains the vestibular folds, and between these and the vocal folds are the laryngeal ventricles.

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Vestibular fold

The vestibular fold is one of two thick folds of mucous membrane, each enclosing a narrow band of fibrous tissue, the vestibular ligament, which is attached in front to the angle of the thyroid cartilage immediately below the attachment of the epiglottis, and behind to the antero-lateral surface of the arytenoid cartilage, a short distance above the vocal process.

Laryngeal ventricle

The laryngeal ventricle, is a fusiform fossa, situated between the vestibular and vocal folds on either side, and extending nearly their entire length. There is also a sinus of Morgagni in the pharynx.

Outline of human anatomy scientific study of the morphology of the human body

The following outline is provided as an overview of and topical guide to human anatomy:

Vocal process

In the human larynx, the vocal process is the anterior angle of the base of the arytenoid cartilage, as it projects horizontally forward and gives attachment to the vocal ligament.

Histology is the study of the minute structure, composition, and function of tissues. Mature human vocal cords are composed of layered structures which are quite different at the histological level.

References

This article incorporates text in the public domain from page 1083 of the 20th edition of Gray's Anatomy (1918)