Which type of vocal fold movement is primarily controlled by the PCA muscle?

The primary role of the posterior cricoarytenoid (PCA) muscle is to facilitate the abduction of the vocal folds. When the PCA muscle contracts, it pulls the vocal folds apart, thereby allowing the airway to open and enabling breathing. This action is crucial for respiration, as it allows air to flow freely through the larynx when the vocal folds are abducted.

Understanding the action of the PCA is important for recognizing how vocal fold movement contributes to various functions such as phonation and respiration. While adduction of the vocal folds involves the action of other muscles that bring the vocal folds together for phonation, the PCA specifically counteracts this by moving the folds apart. Knowing this distinction aids in grasping the overall mechanics of the larynx and its muscular control in speech and breathing contexts.