The cricothyroid muscle is the only tensor muscle of the larynx, aiding with phonation. It attaches to the anterolateral aspect of the cricoid and the inferior cornu and lower lamina of the thyroid cartilage, and its action tilts the thyroid forward to help tense the vocal cords. Not to be confused with the posterior cricoarytenoid muscles, which are the only muscles directly responsible for opening (abducting) the space between the vocal cords to allow for sound production.
The Cricothyroid muscle produces tension and elongation of the vocal folds by drawing up the arch of the cricoid cartilage and tilting back the upper border of the thyroid cartilage lamina; the distance between the vocal processes and the angle of the thyroid is thus increased, and the folds are consequently elongated, resulting in higher pitch phonation.
This muscle is the only laryngeal muscle supplied by the branch of the vagus nerve known as the external branch of the superior laryngeal nerve (rather than the recurrent laryngeal nerve).
The veins of the thyroid gland.
The fascia and middle thyroid veins.
Side view of the larynx, showing muscular attachments.