Certified Registered Nurse Anesthetist (CRNA) Practice Exam

Which is the only abductor muscle of the vocal cords?

1. Thyroarytenoid muscle

2. Cricothyroid muscle

3. Posterior cricoarytenoid muscle

4. Lateral cricoarytenoid muscle

The correct answer is: Posterior cricoarytenoid muscle

The posterior cricoarytenoid muscle is indeed the only abductor muscle of the vocal cords. Its primary function is to open the vocal cords during phonation and quiet breathing. When the posterior cricoarytenoid muscle contracts, it pulls the arytenoid cartilages laterally, which results in the abduction of the vocal folds. This action is essential for allowing air to pass through the glottis freely, enabling normal respiratory function. In contrast, other muscles such as the thyroarytenoid, cricothyroid, and lateral cricoarytenoid play different roles in vocal cord movement. The thyroarytenoid muscle primarily functions as a relaxer of the vocal cords, while the cricothyroid muscle is involved in the elongation and tensing of the vocal cords, helping to modulate pitch. The lateral cricoarytenoid muscle, on the other hand, serves to adduct the vocal cords, bringing them closer together during phonation, which is the opposite action of abduction. Understanding the specific functions of each muscle is crucial for recognizing their contributions to vocal cord dynamics.