Lungs: Facts, Function and Diseases

Lungs are sacks of tissue located just below the rib cage and above the diaphragm. They are an important part of the respiratory system and waste management for the body.

Size

A person's lungs are not the same size. The right lung is a little wider than the left lung, but it is also shorter. According to York University, the right lung is shorter because it has to make room for the liver, which is right beneath it. The left lung is narrower because it must make room for the heart.

Typically, a man's lungs can hold more air than a woman's. At rest, a man's lungs can hold around 750 cubic centimeters (about 1.5 pints) of air, while a woman's can hold around 285 to 393 cc (0.6 to 0.8 pints) of air, according to York University. "The lungs are over-engineered to accomplish the job that we ask them to do," said Dr. Jonathan P. Parsons, a professor of internal medicine, associate director of Clinical Services, and director of the Division of Pulmonary, Allergy, Critical Care and Sleep Medicine at the OSU Asthma Center at The Ohio State University. "In healthy people without chronic lung disease, even at maximum exercise intensity, we only use 70 percent of the possible lung capacity." 

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Function

According to the American Lung Association, adults typically take 15 to 20 breaths a minute, which comes to around 20,000 breaths a day. Babies tend to breath faster than adults. For example, a newborn's normal breathing rate is about 40 times each minute while the average resting respiratory rate for adults is 12 to 16 breaths per minute. [Respiratory System: Facts, Function and Diseases]

Though breathing seems simple, it is a very complex process.

The right lung is divided into three different sections, called lobes. The left lung has just two lobes. The lobes are made of sponge-like tissue that is surrounded by a membrane called pleura, which separates the lungs from the chest wall. Each lung half has its own pleura sack. This is why, when one lung is punctured, the other can go on working. 

The lungs are like bellows. When they expand, they pull air into the body. When they compress, they expel carbon dioxide, a waste gas that bodies produce. Lungs do not have muscles to pump air in and out, though. The diaphragm and rib cage essentially pump the lungs.

As a person breathes, air travels down the throat and into the trachea, also known as the windpipe. The trachea divides into smaller passages called the bronchial tubes. The bronchial tubes go into each lung. The bronchial tubes branch out into smaller subdivisions throughout each side of the lung. The smallest branches are called bronchioles and each bronchiole has an air sac, also called alveoli. There are around 480 million alveoli in the human lungs, according to the Department of Anatomy of the University of Göttingen.

The alveoli have many capillary veins in their walls. Oxygen passes through the alveoli, into the capillaries and into the blood. It is carried to the heart and then pumped throughout the body to the tissues and organs.

As oxygen is going into the bloodstream, carbon dioxide passes from the blood into the alveoli and then makes its journey out of the body. This process is called gas exchange. When a person breathes shallowly, carbon dioxide accumulates inside the body. This accumulation causes yawning, according to York University. 

The lungs have a special way to protect themselves. Cilia, which look like a coating of very small hairs, line the bronchial tubes. The cilia wave back and forth spreading mucus into the throat so that it can be dispelled by the body. Mucus cleans out the lungs and rids them of dust, germs and any other unwanted items that may end up in the lungs. 

Diseases & conditions

The lungs can have a wide range of problems that can stem from genetics, bad habits, an unhealthy diet and viruses. "The most common lung related conditions I see are reactive airways or asthma, as well as smoking-related emphysema, in my general practice," Dr. Jack Jacoub, a medical oncologist and director of thoracic oncology at Memorial Care Cancer Institute at Orange Coast Memorial Medical Center in Fountain Valley, California, told Live Science. 

Asthma, also called reactive airway disease before a diagnosis of asthma, is a lung disease where the air passageways in the lungs become inflamed and narrowed, making it hard to breath. In the United States, more than 25 million people, including 7 million children, have asthma, according to the National Heart, Lung, and Blood Institute.

Lung cancer is cancer that originates in the lungs. It is the No. 1 cause of deaths from cancer in the United States for both men and women, according to the Mayo Clinic. Symptoms of cancer include coughing up blood, a cough that doesn't go away, shortness of breath, wheezing, chest pain, headaches, hoarseness, weight loss and bone pain.

Chronic obstructive pulmonary disease (COPD) is long-term lung disease that prevents a person from breathing properly due to excess mucus or the degeneration of the lungs. Chronic bronchitis and emphysema are considered COPD diseases. About 11.4 million people in the United States suffer from COPD, with about 80 to 90 percent of COPD deaths attributed to smoking, according to the American Cancer Society. 

Sometimes, those with COPD get lung transplants, replacement lungs garnered from organ donors, to save their lives. Research is also being done on growing new lungs from stem cells. Currently, stem cells extracted from the patient's blood or bone marrow are being used as a treatment to heal damaged lung tissue.

Lung infections, such as bronchitis or pneumonia, are usually caused by viruses, but can also be caused by fungal organisms or bacteria, according to Ohio State University. Some severe or chronic lung infections can cause fluid in the lungs and other symptoms such as swollen lymph nodes, coughing up blood and a persistent fever. 

Being overweight can also affect the lungs. "Yes, being overweight does adversely affect the lungs because it increases the work and energy expenditure to breath," said Jacoub. "In the most extreme form, it acts like a constricting process or vest around the chest such as that seen in the 'Pickwickian syndrome.'"

Promoting good lung health

One of the best ways to promote good lung health is to avoid cigarette smoke because at least 70 out of the 7,000 chemicals in cigarette smoke damages the cells within the lungs. According to the Mayo Clinic, people who smoke have the greatest risk of lung cancer. The more a person smokes, the greater the risk. Those who smoke are 15 to 30 times more likely to get lung cancer according to the Centers for Disease Control and Prevention. If a person quits, their lungs can heal from much of the damage, said Dr. Norman Edelman, a senior scientific adviser for the American Lung Association and a specialist in pulmonary medicine. [Do Smokers' Lungs Heal After They Quit?]

The Rush University Medical Center also suggests practicing deep breathing exercises, staying hydrated and regular exercise to keep the lungs healthy. Parsons also recommends having homes tested for radon. "Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in the ground. It typically leaks into a house through cracks in the foundation and walls. Radon is the main cause of lung cancer in nonsmokers, and the second-leading cause of the disease after smoking," said Parsons.

Additional resources

• American Lung Association
• Taylor and Francis Online: Experimental Lung Research
• Lung Institute: Stem Cell Therapy for Lung Disease
• Scientific American: If a person's lung size cannot increase, how does exercise serve to improve lung function?
• National Institute of Health: Variability in the size of airspaces in normal human lungs as estimated by aerosols