Healthy lungs deliver oxygen to and remove carbon dioxide from the body. Unlike other internal organs, healthy lungs are routinely and directly touched by the outside environment through the air breathed in. The delicate tissues of the lungs must defend against germs, tobacco smoke and harmful air pollutants that can damage airways and inhibit lung function.
Each healthy lung is 10 to 12 inches long and appears pink and sponge-like. To make room for the heart between the two lungs inside the chest cavity, the left lung is slightly smaller than the right lung and has two lobes instead of the three lobes on the right lung. The rib cage, made up of 12 sets of ribs, protects the lungs. Located beneath the lungs, the diaphragm muscle helps the lungs inhale and exhale air.
Each breath enters the nose or mouth and down the trachea or windpipe into two large airways called bronchi that lead to the right and left lungs. After entering the lungs, air progresses through 22 smaller tubes to reach the 100,000 very smallest tubes called bronchioles. From there, air travels to the 1,000,000 alveoli or tiny air sacs that resemble clusters of grapes
Healthy lungs breathe 12 to 18 times per minute or 20,000 times per day, according to the American Association of Respiratory Care, helping to keep the body working normally. Each breath brings in about a pint of air and adds oxygen to the blood which then carries it to every cell in the body. Oxygen helps cells function, participates in many chemical reactions and helps repair injured tissues.
The maximum amount of air a person can inhale and exhale in one breath, called vital capacity, relates to life expectancy. Smoking, air pollution, exercise, obesity, posture and shallow breathing can affect vital capacity and the amount of air delivered to the body.
To avoid life-threatening consequences, the body must keep the blood and other fluids within a narrow range of acidity. Healthy lungs play an essential role in maintaining this balance by regulating how much carbon dioxide is breathed out according to Eleanor Whitney and Sharon Rolfes in the text "Understanding Nutrition." Breathing speeds up when too much carbon dioxide causes the fluids to become too acid and slows down when the fluids become too basic.