The windpipe begins by extending downward from a structure that contains the vocal cords referred to as the larynx -- more commonly known as voice box or Adam's apple. When exercising the skill of speech, the chords vibrate as air passes over them to produce sound. Close behind the windpipe is another long tube referred to as the esophagus that provides passage for food and drink to the stomach. In order to prevent food from entering the air passages of the larynx and trachea, a leaf-shaped flap of tissue, the epiglottis, closes the opening into the larynx during swallowing. The human trachea is about five inches long and about half of its length extends into the chest cavity and the rest is in the neck. The windpipe eventually branches into two principal bronchi, one for the right lung and one for the left, which extend and refine before connecting to lung tissue to transfer oxygen.