Phonation occurs when the intrinsic laryngeal muscles close (= adduct) the
glottis and air is forced up between the vocal folds from the lungs. The moving
air causes the folds to vibrate and sounds to be produced. The intrinsic muscles
adjust the position and tension of the vocal folds by moving the arytenoid
cartilages. The pyramidal-shaped arytenoid cartilages sit on top of the lamina
(back plate) of the cricoid cartilage. When the intrinsic muscles contract,
they rotate the arytenoid cartilages and slide them medially (adduction), laterally
(abduction), and anteriorly. As they move, the arytenoid cartilages pull on
the attached vocal folds.
Voice pitch is determined by the tension applied to the vocal folds by the
arythenoid cartilages. Pitch increases when the cricothyroid muscles move the
arytenoids back and the vocal folds are tightened. Pitch decreases when the
vocalis and thyroarytenoid muscles move the arytenoids forward and the vocal
folds are loosened.
