The trachea is around 15 centimetres long, we move our way down. There's a difference anatomically between the left and right main stem bronchi. They are wider and more vertical but still have cartilage associated with them. The airways will branch and branch and branch at about 23 separate times. And when it does this, they get more numerous but smaller in diameter. We'll get to this point later - Matthew explains why you might want to widen your trachea.