Which structure is not involved in the movement of the arytenoid cartilages?

The movement of the arytenoid cartilages is crucial for vocal fold function. The correct answer highlights that rotational movement is not a typical component involved in the mechanics of arytenoid cartilages.

The arytenoid cartilages primarily engage in movements characterized by rocking, gliding (or sliding), and some degree of rotation in a limited aspect; however, "rotational movement" implies a significant pivot around a central axis, which doesn't accurately describe the manner in which they move during phonation or adduction/abduction of the vocal folds.

The rocking motion refers to the arytenoids tilting forward and backward, which adjusts the tension on the vocal folds to control pitch. Gliding movements enable the cartilages to move horizontally to bring the vocal folds together or apart. These types of movement are essential for the modulation of speech and sound production.

In contrast, the idea of the arytenoids undergoing significant rotational movement does not align with their anatomical design or the functional requirements involved in laryngeal adjustments, which further solidifies why the alternative options correctly illustrate the actions taking place instead of implying a broader rotational action.