The vocal folds, also known popularly as vocal cords, are composed of twin infoldings of
mucous membrane stretched horizontally across the
larynx. They
vibrate, modulating the flow of air being expelled from the lungs during
phonation. Open during inhalation, closed when holding one's breath, and vibrating for speech or singing (opening and closing 440 times per second when singing A above
middle C); the folds are controlled via the vagus nerve. They are white because of scant blood circulation.
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Two small bands of muscle within the larynx. They close to prevent food from getting into the lungs, and they vibrate to produce the voice.