Certified Registered Nurse Anesthetist (CRNA) Practice Exam

Which is the only muscle of the larynx supplied by the superior laryngeal nerve?

1. Interarytenoid muscle

2. Cricothyroid muscle

3. Posterior cricoarytenoid muscle

4. Lateral cricoarytenoid muscle

The correct answer is: Cricothyroid muscle

The cricothyroid muscle is the only laryngeal muscle innervated by the superior laryngeal nerve, specifically through its external branch. This nerve is responsible for controlling the pitch of the voice by tensing the vocal cords; when the cricothyroid muscle contracts, it tilts the thyroid cartilage forward and downward, stretching the vocal cords and thereby increasing pitch. In contrast, the other muscles of the larynx listed are innervated by the recurrent laryngeal nerve, which branches from the vagus nerve. These include the interarytenoid muscle, which helps in adducting the vocal folds, and the posterior cricoarytenoid and lateral cricoarytenoid muscles, which also play roles in abduction and adduction of the vocal cords, respectively. Understanding the specific innervation of these muscles is crucial for anesthetic management in procedures involving the airway, emphasizing the importance of the cricothyroid muscle’s unique innervation by the superior laryngeal nerve.