Muscle
Cricothyroid
Changes vocal-fold length from outside the laryngeal cavity
High-yield
Among the intrinsic laryngeal muscles, cricothyroid has the characteristic external superior laryngeal nerve supply. Its superficial position does not make it the only muscle outside the larynx; the extrinsic muscles also lie outside it.
Overview
Cricothyroid spans the outer surfaces of the cricoid and thyroid cartilages. Its straight and oblique parts alter their relative position, increasing the distance between the anterior and posterior vocal-fold attachments. The resulting lengthening and tension help raise vocal pitch.
Reference facts
- Origin
- Anterior and lateral parts of the cricoid arch.
- Insertion
- Inferior thyroid-cartilage border and inferior horn, through straight and oblique portions.
- Innervation
- External branch of the superior laryngeal nerve, from CN X; additional communicating fibers are anatomical variants.
- Action
- Changes the thyroid–cricoid angle to lengthen and tense the vocal folds, contributing to higher pitch.
- Blood supply
- Predominantly the cricothyroid branch of the superior thyroid artery.
Mnemonic
Cricothyroid stretches the cords; the external superior laryngeal branch supplies it.
Clinical correlation
The external superior laryngeal nerve passes near vessels at the upper thyroid pole and can be injured during thyroid surgery. Cricothyroid weakness may reduce upper pitch range or cause vocal fatigue; the voice change is not always a uniform monotone.
Frequently asked questions
What does the cricothyroid do?
The cricothyroid changes the thyroid–cricoid angle to lengthen and tense the vocal folds, contributing to higher pitch.
What nerve innervates the cricothyroid?
External branch of the superior laryngeal nerve, from CN X; additional communicating fibers are anatomical variants.
Where does the cricothyroid attach?
Origin: Anterior and lateral parts of the cricoid arch. Insertion: Inferior thyroid-cartilage border and inferior horn, through straight and oblique portions.
What is the blood supply of the cricothyroid?
Predominantly the cricothyroid branch of the superior thyroid artery.