Which group of muscles includes both thyrovocalis and thyromuscularis muscle?

The correct answer is the group of muscles called the thyroarytenoid. This group includes both the thyrovocalis and the thyromuscularis muscles, which are crucial components of the laryngeal structure and vocal fold function.

The thyrovocalis muscle is the medial part of the thyroarytenoid muscle that primarily functions in adjusting the tension of the vocal folds, thereby modulating pitch during phonation. In contrast, the thyromuscularis muscle is the lateral part that helps in the relaxation of the vocal folds and assists in controlling the airflow during speech and other vocalizations. Together, these muscles contribute significantly to the mechanics of voice production by affecting the length and tension of the vocal cords.

Understanding the role of the thyroarytenoid muscle group in laryngeal function is essential for comprehending how phonation occurs, as well as the muscular coordination involved in speech and voice modulation. The other groups of muscles mentioned in the choices do not contain both the thyrovocalis and thyromuscularis, which clarifies why they do not represent the correct answer.