By taking in oxygen from the air and expelling carbon dioxide, the lungs play a crucial role in maintaining life. The oxygen gathered by the lungs enters the blood as it circulates and is distributed to cells throughout the body. Of all the body's organs, the lungs, which are not yet fully mature at birth, account for the greatest number of health problems in infants and young children, including viral and bacterial infections, asthma, and obstruction from swallowing or inhaling foreign objects and substances.

During the prenatal stage, the lungs are among the last organs to finish developing. The surfactant coating that keeps them from sticking together isn't formed until the last month or two of gestation. The air sacs (alveoli) at the ends of the bronchial tubes are formed last and continue developing for some time after birth: the...