When relaxed, the vocal cords normally form a V-shaped opening that allows air to pass freely through to the trachea. The cords open when air is drawn into the lungs (inspiration) and close during swallowing or speech. Holding a mirror in the back of a person's mouth, a specially trained doctor can often see the vocal cords and check for problems, such as contact ulcers, polyps, nodules, granulomas (not shown), paralysis, and cancer. All of these problems affect the voice. Paralysis may affect one (one-sided) or both vocal cords (two-sided—not shown).