The vocal folds are to separate structures which are located in the larynx or voice box. Humans have two vocal folds which open and close during normal breathing, and during sound production, or phonation, the vocal folds come together and vibrate.
The vocal folds are intricately layered, which is the reason for unique sound production. The outer layer is squamous, non-keratinizng epithelium. Just deep to this is the superficial layer of the lamina propria. This is a gel like layer, which allows the vocal fold to vibrate and produce sound. The deeper layers of the vocal fold are muscles – the vocalis and thyroarytenoid muscles make up the deepest portion of the vocal fold.