This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: ENT
Vocal cords are abducted by: March 2003 
Select and explain. 
A. Cricothyroid, B. Posterior crico-arytenoid, C. Lateral crico-arytenoid, D. Thyro-arytenoid
B: Posterior crico-arytenoid
Answer: B: Posterior crico-arytenoid 
Explanation: Ans. B i.e. Posterior crico-arytenoid USCLES ORIGIN INSEION INNERVATION ACTION Cricothyroid (Located on external aspect) Anterolateral pa of cricoid cailage Inferior margin & inferior horn of thyroid cailage External laryngeal stretches & tenses vocal fold Post. cricoarytenoid (Safety muscle of larynx) Post. surface of lamina of cricoid cailage Muscular process of arytenoid cailage Reccurent laryngeal Abduct vocal fold Tensor of vocal cord during phonation Lateral cricoarytenoid Arch of cricoid cailage Muscular process of arytenoid cailage Reccurent laryngeal Adduct vocal fold Arytenoid transverse/interarytenoid oblique fibers One arytenoid cailage Another arytenoid cailage Reccurent laryngeal Close intercailagenous pa of rima glottidis Adduct vocal cord control laryngeal inlet Thyroarytenoid Post. surface of thyroid cailage Muscular process of arytenoid cailage Reccurent laryngeal Adduct vocal cord Vocalis Depression b/w laminae of thyroid cailage Pa of vocal ligament & vocal process of arytenoid cailage Reccurent laryngeal Relaxes pot. vocal ligament while maintaining tension of ant. pa