The external branch of the superior laryngeal nerve innervates which muscle?

• A. Cricothyroid
• B. Posterior Cricoarytenoid
• C. Lateral Cricoarytenoid
• D. Interarytenoid

Answer: (A)

The main idea here is that the external branch of the superior laryngeal nerve has a unique motor role among the laryngeal nerves: it innervates only the cricothyroid muscle. The cricothyroid tensionizes the vocal folds by tilting the thyroid cartilage forward, which lengthens and tightens the vocal cords and raises pitch. The other muscles listed—the posterior cricoarytenoid, the lateral cricoarytenoid, and the interarytenoids—are innervated by the recurrent laryngeal nerve and have different functions (for example, the posterior cricoarytenoid abducts the vocal folds, while the others mainly adduct or adjust tension). So, the muscle fed by the external branch that adjusts tension and pitch is cricothyroid.