visualize the complex horizontal and vertical movements of vocal folds. the vocal folds generate a sound rich in harmonics. the harmonics are produced by collisions of the vocal folds with themselves, by recirculation of some of the air back through the trachea, or both. some singers can isolate some of those harmonics in a way that is perceived as singing in more than one pitch at the same time—a technique called overtone singing or throat singing such as in the tradition of tuvan throat singing. clinical significance lesions the majority of vocal fold lesions primarily arise in the cover of the folds. since the basal lamina secures the epithelium to the superficial layer of the lamina propria with anchoring fibers, this is a common site for injury. if a person has a phonotrauma or habitual vocal hyperfunction, also known as pressed phonation, the proteins in the basal lamina can shear, causing vocal fold injury, usually seen as nodules or polyps, which increase the mass and thickness of the cover. the squamous cell epithelium of the anterior glottis are also a frequent site of laryngeal cancer caused by smoking. reinke's edema a voice pathology called reinke's edema, swelling due to abnormal accumulation of fluid, occurs in the superficial lamina propria or reinke's space. this causes the vocal fold mucosa to appear floppy with excessive movement of the cover that has been described as looking like a loose sock. the greater mass of the vocal folds due to increased fluid lowers the fundamental frequency during phonation. wound healing wound healing is a natural regeneration process of dermal and epidermal tissue involving a sequence of biochemical events. these events are complex and can be categorized into three stages: inflammation, proliferation and tissue remodeling. the study on vocal fold wound healing is not as extensive as that on animal models due to the limited availability of human vocal folds. vocal fold injuries can have a number of causes including chronic overuse, chemical, thermal and mechanical trauma such as smoking, laryngeal cancer, and surgery. other benign pathological phenomena like polyps, vocal fold nodules and edema will also introduce disordered phonation. any injury to human vocal folds elicits a wound healing process characterized by disorganized collagen deposition and, eventually, formation of scar tissue. verdolini and her group sought to detect and describe acute tissue response of injured rabbit vocal cord model. they quantified the expression of two biochemical markers: interleukin 1 and prostaglandin e2, which are associated with acute wound healing. they found the secretions of these inflammatory mediators were significantly elevated when collected from injured vocal cords versus normal vocal cords. this result was consistent with their previous study about the function of il-1 and pge-2 in wound healing. investigation about the temporal and magnitude of inflammatory response in the vocal cords may benefit for elucidating subsequent pathological events in vocal fold wounding, which is good for clinician to develop therapeutic targets to minimize scar formation. in the proliferative phase of vocal cord wound healing, if the production of hyaluronic acid and collagen is not balanced, which means the hyaluronic acid level is lower than normal, the fibrosis of collagen cannot be regulated. consequently, regenerative-type wound healing turns to be the formation of scar. scarring may lead to the deformity of vocal fold edge, the disruption of lipopolysaccharides viscosity and stiffness. patients suffering from vocal fold scar complain about increased phonatory effort, vocal fatigue, breathlessness, and dysphonia. vocal fold scar is one of the most challenging problems for otolaryngologists because it is hard to be diagnosed at germinal stage and the function necessity of vocal cords is delicate. terminology the vocal folds are commonly referred to as vocal cords, and less commonly as vocal flaps or vocal bands. the term vocal cords was coined by the french anatomist antoine ferrein in 1741. in his violin analogy of the human voice, he postulated that the moving air acted like a bow on cordes vocales. the alternative spelling in english is vocal chords, possibly due to the musical connotations or to confusion with the geometrical definition of the word chord. while both spellings have historical precedents, standard american spelling is cords. according to the oxford english corpus, a database of 21st-century texts that contains everything from academic journal articles to unedited writing and blog entries, contemporary writers opt for the nonstandard chords instead of cords 49% of the time. the cords spelling is also standard in the united kingdom and australia. in phonetics, vocal folds is preferred over vocal cords, on the grounds that it is more accurate and illustrative.