American Board of Surgery Qualifying Exam (ABS QE) Practice Test

Which muscle is innervated by the superior laryngeal nerve?

1. Cricothyroid muscle

2. Thyrohyoid muscle

3. Vocalis muscle

4. Oblique arytenoid muscle

The correct answer is: Cricothyroid muscle

The superior laryngeal nerve, a branch of the vagus nerve, is primarily responsible for the innervation of the cricothyroid muscle. This muscle plays a crucial role in modulating pitch by tensing the vocal cords. When the cricothyroid muscle contracts, it pulls the thyroid cartilage forward and downward, which stretches the vocal cords, increasing their tension and allowing for higher pitch sounds during phonation. In contrast, the other muscles listed have different innervation sources. The thyrohyoid muscle, for example, is innervated by the ansa cervicalis and plays a part in the elevation of the larynx during swallowing. The vocalis muscle, which is involved in fine-tuning the tension of the vocal cords for sound production, is innervated by the recurrent laryngeal nerve. Lastly, the oblique arytenoid muscle, part of the intrinsic laryngeal muscles responsible for adducting the vocal cords, is also innervated by the recurrent laryngeal nerve. Thus, recognizing the specific nerve that innervates the cricothyroid muscle is vital for understanding its function in speech and related anatomical relationships.