The external laryngeal nerve is a branch of the superior laryngeal nerve, which itself is a part of the vagus nerve. This nerve primarily innervates the cricothyroid muscle, playing a crucial role in adjusting the tension of the vocal cords, which affects pitch during speech. Injury to the external laryngeal nerve can lead to voice changes, such as a weak or hoarse voice, due to impaired control of the vocal cords. Understanding its function is important in fields like otolaryngology and speech therapy, where vocal health is a key focus.