Cricothyroid (Straight Part)
Larynx · Head & Neck
The cricothyroid is the only intrinsic laryngeal muscle to lie on the outer surface of the larynx, and its straight (vertical) part is the more anterior of its two divisions. It arises from the anterolateral arch of the cricoid cartilage and runs almost vertically upward to insert on the lower margin of the thyroid lamina. By tilting the thyroid cartilage forward and downward on the cricothyroid joint, it lengthens and tenses the vocal folds, which raises the pitch of the voice. It is the sole intrinsic laryngeal muscle supplied by the external laryngeal branch of the superior laryngeal nerve (from the vagus, CN X), rather than the recurrent laryngeal nerve. This unique innervation makes it the muscle at risk during thyroid surgery near the superior thyroid vessels.
Origin, Insertion, Action & Nerve
Origin
Anterolateral arch of the cricoid cartilage
Insertion
Lower margin of the thyroid lamina
Action
Tenses and elongates the vocal folds, raising vocal pitch
Nerve
External laryngeal branch of the superior laryngeal nerve (vagus, CN X)
Attachments explained
The Cricothyroid (Straight 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
Anterolateral arch of the cricoid cartilage
Insertion
Lower margin of the thyroid lamina
Action & function
When the Cricothyroid (Straight Part) contracts, it produces the following movement: Tenses and elongates the vocal folds, raising vocal pitch.
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 Cricothyroid (Straight Part) receives its nerve supply from the External laryngeal branch of the superior laryngeal nerve (vagus, CN X).
Because a muscle can only contract when its nerve is intact, injury to the External laryngeal branch of the superior laryngeal nerve can weaken or paralyse the Cricothyroid (Straight Part), impairing the movements it normally produces (tenses and elongates the vocal folds, raising vocal pitch). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Cricothyroid (Straight Part) (the OIANS method)
Learn the straight part as the near-vertical belly that runs straight up from the cricoid arch to the underside of the thyroid lamina. Its almost upright fibres pull the thyroid cartilage forward, stretching the vocal folds, so linking its vertical line of pull to elongation and higher pitch makes the action self-evident.
Make the nerve the headline fact: cricothyroid is the one intrinsic laryngeal muscle supplied by the external laryngeal nerve, while every other intrinsic muscle relies on the recurrent laryngeal nerve. Because this nerve runs beside the superior thyroid artery, injury during thyroidectomy weakens the voice's ability to reach high notes, a clinical hook that ties origin, action, and nerve together.
Frequently asked questions
Where is the Cricothyroid (Straight Part) located?
The Cricothyroid (Straight Part) is a muscle of the Larynx group, located in the Head & Neck.
What is the origin of the Cricothyroid (Straight Part)?
Anterolateral arch of the cricoid cartilage
What is the insertion of the Cricothyroid (Straight Part)?
Lower margin of the thyroid lamina
What movements does the Cricothyroid (Straight Part) produce?
Tenses and elongates the vocal folds, raising vocal pitch
What nerve supplies the Cricothyroid (Straight Part)?
External laryngeal branch of the superior laryngeal nerve (vagus, CN X)
Is the Cricothyroid (Straight Part) free to study in OIANS?
The Cricothyroid (Straight 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.
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Study the Cricothyroid (Straight Part)
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