Which of the following muscle produces abduction of vocal cord? (D. REPEAT 2013)

Ref: Gray's Anatomy, 39th edition, 2008. Page 642Explanation:Posterior CricoarytenoidThe only muscle produce abduction of vocal cord (open the rima glottides).Called the safety muscle of larynx.Origin: posterior surface of lamina of cricoid cartilage.Insertion: muscular process of arytenoid cartilage.Nerve supply: recurrent laryngeal nerve (branch of vagus).Blood supply: laryngeal branches of superior and inferior thyroid arteries.Muscles Acting at Vocal CordActionMuscleAbductor* Posterior cricoarytenoidAdductor "TIL AC"* Thyroarytenoid* Interarytenoid* Lateral CricoarytenoidTensor of vocal cord* Cricothyroid* ThyroarytenoidOpeners of laryngeal inlet* ThyroepiglottisClosers of laryngeal inlet* Inter arytenoid* AryepiglottisNERVE SUPPLY OF LARYNGEAL MUSCLESMotor* All intrinsic muscles of the larynx is supplied by recurrent laryngeal nerve except for cricothyroid which is supplied by external laryngeal nerve. Sensory* Upto the level of vocal fold is supplied by internal laryngeal nerve.* Below the level of vocal cord is supplied by recurrent laryngeal nerve.