There are two vocal folds: right and left. They are sometimes know as the ‘true vocal folds’ to distinguish them from the false folds. They are also known as the vocal cords. This term stems from the time when they were thought to vibrate like strings. The vocal fold is the anterior part of the ‘vocal cord’ that vibrates.  The vocal folds are foldings of mucous membrane which vibrate modulating the flow of air from the lungs during phonation. Histologically the vibrating portion of the vocal fold known as the membranous part. From a mechanical point of view the vocal fold consists of a cover layer (epithelium, superficial lamina propria) a transition layer (intermediate lamina propria and deep lamina propria) and body (vocalis muscle).  The vocalis part of the thyroarytenoid muscle inserts in to the deep layer of the lamina propria which is firmly attached to the vocal process posteriorly, the thyroid cartilage anteriorly.