Thyroarytenoid (External Part)
Larynx · Head & Neck
The external part is the main, broad body of the thyroarytenoid muscle, forming the bulk of the muscle lateral to the vocalis and the vocal ligament. It arises from the inner surface of the thyroid lamina and passes backward to insert on the muscular process and lateral surface of the arytenoid cartilage. Its contraction shortens and relaxes the vocal folds and, by rotating the arytenoid, adducts the folds and helps close the rima glottidis. It is innervated by the recurrent laryngeal nerve (vagus, CN X). Together with vocalis it constitutes the thyroarytenoid complex that both relaxes and approximates the folds.
Origin, Insertion, Action & Nerve
Origin
Inner surface of the thyroid lamina
Insertion
Muscular process and lateral surface of the arytenoid cartilage
Action
Shortens and relaxes the vocal folds; adducts and aids closure of the rima glottidis
Nerve
Recurrent laryngeal nerve (vagus, CN X)
Attachments explained
The Thyroarytenoid (External Part) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Inner surface of the thyroid lamina
Insertion
Muscular process and lateral surface of the arytenoid cartilage
Action & function
When the Thyroarytenoid (External Part) contracts, it produces the following movements: Shortens and relaxes the vocal folds; adducts and aids closure of the rima glottidis.
As part of the Larynx group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Thyroarytenoid (External Part) receives its nerve supply from the Recurrent laryngeal nerve (vagus, CN X).
Because a muscle can only contract when its nerve is intact, injury to the Recurrent laryngeal nerve can weaken or paralyse the Thyroarytenoid (External Part), impairing the movements it normally produces (shortens and relaxes the vocal folds). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Thyroarytenoid (External Part) (the OIANS method)
Fix the external part as the outer, meatier portion of thyroarytenoid, running from the thyroid lamina to the muscular process of the arytenoid. Because it grips the muscular process, it can swing the arytenoid to bring the folds together while its bulk shortens them, so it both adducts and slackens the folds.
Pair it with vocalis as the two halves of thyroarytenoid: vocalis is the fine medial tuner within the fold, the external part is the coarse lateral shortener and adductor. Both answer to the recurrent laryngeal nerve, and remembering that thyroarytenoid as a whole shortens the folds distinguishes it cleanly from the lengthening cricothyroid.
Frequently asked questions
Where is the Thyroarytenoid (External Part) located?
The Thyroarytenoid (External Part) is a muscle of the Larynx group, located in the Head & Neck.
What is the origin of the Thyroarytenoid (External Part)?
Inner surface of the thyroid lamina
What is the insertion of the Thyroarytenoid (External Part)?
Muscular process and lateral surface of the arytenoid cartilage
What movements does the Thyroarytenoid (External Part) produce?
Shortens and relaxes the vocal folds; adducts and aids closure of the rima glottidis
What nerve supplies the Thyroarytenoid (External Part)?
Recurrent laryngeal nerve (vagus, CN X)
Is the Thyroarytenoid (External Part) free to study in OIANS?
The Thyroarytenoid (External Part) is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Head & Neck is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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