What is chronic bronchitis? What is the difference between chronic bronchitis and COPD?

The lung has a series of branching tubes that deliver air to and from the atmosphere to the alveoli. These tubes are called bronchi. The cells that line the bronchi are made up of special cells with hairy filaments on them called cilia, as well as special cells that secrete mucus. The function of these cells is to protect the lung from pollutants, allergens, and micro-organism that we inhale from the environment. ...