Thyroarytenoid

The thyroarytenoid is an intrinsic muscle of the larynx that forms the bulk of the vocal folds. It runs from the inner surface of the thyroid cartilage to the arytenoid cartilages, and lies adjacent to the vocal ligament.

The muscle is subdivided into two parts: the thyrovocalis (internal thyroarytenoid) and the thyromuscularis (external thyroarytenoid). The thyrovocalis attaches to the vocal process of the arytenoid, whereas the thyromuscularis inserts into the muscular process. Together, these portions modulate vocal fold tension and length.

Functionally, contraction of the thyroarytenoid tends to shorten and thicken the vocal folds, reducing their tension and lowering perceived pitch. This action provides a counterbalance to the cricothyroid muscle, which lengthens and tenses the folds to raise pitch. The thyroarytenoid also contributes to medial compression and adduction of the vocal folds during phonation, influencing vocal quality and intensity. The two parts can have differing effects: the vocalis portion is associated with increased stiffness and fine-tuning of tension, while the muscular portion can alter bulk and relaxation dynamics of the vocal fold body.

Clinical relevance includes its role in normal voice production and its involvement in disorders of pitch control and glottic closure. Dysfunctions such as paresis or paralysis can lead to hoarseness, breathiness, or reduced voice range, reflecting the muscle’s importance in pitch and voice quality.