The larynx or voicebox protects the trachea of animals and is also vital in the production of sounds.  It is found in all mammals but in humans it sits somewhat higher in the neck.  This allows humans to make a wide range of sounds with the vocal cords in the larynx at the expense of preventing both the trachea and the esophagus to function simultaneously.  For example, in most mammals, it is possible to swallow and breathe simultaneously. 

The larynx is built on nine rings made of cartilage, which are connected to the hyoid bone.  The combination of muscles in the larynx allows the vocal cords to be manipulated in many ways, allowing a human to produce sounds of many different pitches.  The natural pitch of the voice depends on the size of the vocal cords, with voices in the lower range having larger folds and in the higher range having smaller folds.  As such, men tend to have lower pitched voices than women because of their larger larynx.

Damage to the folds, nerves and muscles of the larynx can lead to great difficulty speaking or the inability to speak at all.  In Control, House meets a mute patient in the clinic who he eventually diagnoses with a paralyzed larynx, the result of a rare complication of intubation during routine surgery.  In Words and Deeds, the patient's voice rises in pitch and House traces this to interference with the nerves that lead to the larynx.

Larynx at Wikipedia

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