What is the primary function of the Posterior Cricoarytenoid (PCA) muscles?

The primary function of the Posterior Cricoarytenoid (PCA) muscles is to pull the muscular process of the arytenoids posteriorly. This action is crucial because the PCA muscles are the only intrinsic laryngeal muscles responsible for abduction of the vocal cords. When they contract, they rotate the arytenoid cartilages and move them away from the midline, thereby opening the glottis and allowing airflow during breathing. This abduction is essential for proper respiratory function and vocalization, as it facilitates the movement of air through the larynx and aids in phonation by adjusting vocal cord tension and position.

Other muscles in the larynx have different roles, such as adduction or tension adjustment, but the distinct role of the PCA in abduction is vital in ensuring adequate airflow and maintaining normal respiratory mechanics. Thus, the effect of the PCA's contraction is directly linked to its action in pulling the muscular processes of the arytenoids posteriorly.