Lung Structure

• When you breathe in through your mouth or nose, the air you take in is transported to your lungs through a tube called the trachea, or windpipe. The trachea splits into two tubes, called the bronchi, which lead to your two football-sized lungs. Each of the bronchi splits into even smaller tubes called bronchioles, leading to different parts of the lung. Bronchioles break into even tinier tubes called alveoli, which are covered with tiny blood vessels called capillaries.
  
  

Lung Function

• The purpose of our lungs is the exchange of gases. Our bodies need oxygen in order to function. We also need to expel, or breathe out, carbon dioxide. These functions are performed in the lungs. The blood is oxygenated in the alveoli, and carbon dioxide is removed from blood cells to be exhaled. A membrane underneath our lungs called the diaphragm contracts when we breathe in, and expands so we can push air back out. All of this is controlled unconsciously by a center in our brains.
  
  

Capacity

• Our lungs are never truly empty of air, even after we feel as though we have breathed out as deeply as possible. Typical lung capacity measurements do not take into account the liter or so of air that always remains in our lungs. An average adult has a lung capacity of about four and a half liters. Adults have a greater capacity than children; males typically have a greater capacity than females. The tool used to measure lung capacity is called a spirometer.
  
  

Health

• The quality of the air we put into our lungs can greatly affect their efficiency and overall health. Polluted air or cigarette smoke impair our lungs' ability to function at their peak. Diseases like asthma, bronchitis and emphysema will also affect lung capacity, in all instances making it more difficult for our lungs to function.
  
  

Improving Your Lung Capacity

• A highly trained athlete may have a lung capacity as great at six and a half liters, nearly 50 percent greater than an average adult. Our lungs can be trained over time to take in more oxygen as our bodies need it. Exercise that improves lung capacity is called aerobic exercise. Increasing the capacity of your lungs will mean that you need to breathe fewer times in a minute for your body to receive the same amount of oxygen as a person with smaller lung capacity.