The rigid complex of mucosa-covered cartilage and muscle at the cranial aspect of the trachea acts largely and usually effectively to protect the airway from aspiration of unwelcome materials. These 5 laryngeal cartilages also coordinate to modulate airflow during increased exertion, expectoration, coughing, increased mtra-abdominal pressure, and vocalization (more critical in some species than others). The rima glottidis airflow is controlled by active abduction or adduction of the paired arytenoidsdorsally and tensing of the vocal cords ventrally. Further fortification against aspiration during swallowing is obtained by passive caudal movement of the hinged epiglottis. The only true abductor of the intrinsic laryngeal muscles is the dorsal cricoarytenoideus muscle.
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