What are the two compartments of the thyroarytenoid (TA) muscle, and where are they located?

• A. Thyrovocalis: medial belly; Thyromuscularis: lateral belly
• B. Thyrovocalis: lateral belly; Thyromuscularis: medial belly
• C. Lateral thyroarytenoid; Medial thyroarytenoid
• D. Anterior and posterior TA

Answer: (A)

The TA muscle is split into two compartments that reflect its two functional parts: a medial portion called the thyrovocalis (vocalis) and a lateral portion called the thyromuscularis (muscularis). The medial belly lies closest to the midline and attaches toward the vocal process of the arytenoid, making it the tense, vocal fold–lengthening component. The lateral belly is the more lateral part, attaching toward the muscular process of the arytenoid, and contributes to the bulk and adjustment of tension. This arrangement explains why the medial part is associated with vocal fold tension, while the lateral part modulates muscle activity more laterally.