The ability to breathe is easy to take for granted, but many people have medical conditions that make breathing difficult. In most of these cases, those who have trouble breathing have a problem with their respiratory system.
The respiratory system is the part of the body responsible for inhaling and exhaling air and absorbing energy-producing oxygen. The respiratory system includes the lungs, bronchi, trachea, larynx, pharynx, and nose. Much of the function of the respiratory system is connected with the circulatory system, which contains the heart and blood vessels.