Knowing the Basics

How Do Your Lungs Work

American Lung Association Open Airways For Schools program

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Your lungs are part of a group of organs and tissues that all work together to help you breathe. This system is called the respiratory system. The main job of the respiratory system is to move fresh air into and get waste gases out of the body. Oxygen, a basic gas, is needed by every cell in your body in order to live. The air that comes into the body through the lungs contains oxygen and other gases. In the lungs, the oxygen is moved into the bloodstream and carried through the body. At each cell in the body, the oxygen cells are exchanged for waste gas called carbon dioxide. The bloodstream then carries this waste gas back to the lungs where the waste gas is removed from the blood stream and then exhaled from the body. This vital process, called gas exchange, is performed automatically by the lungs and respiratory system.

The right lung is divided into three lobes, or sections. Each lobe is like a balloon filled with sponge-like tissue. Air moves in and out through one opening -- a branch of the bronchial tube.

The left lung is divided into two lobes.

The pleura are the two membranes, actually one continuous one folded on itself, that surround each lobe of the lungs and separate the lungs from the chest wall.

The bronchial tubes are lined with ciliaTiny hairs that sweep fluids and foreign particles out of the airway so that they stay out of the lungs. (like very small hairs) that have a wave-like motion. This motion carries mucusA thick, slippery fluid made by the membranes that line certain organs of the body, like the lungs. It collects unwanted matter like dust and germs. (sticky phlegm or liquid) upward and out into the throat, where it is either coughed up or swallowed. The mucus catches and holds much of the dust, germs, and other unwanted matter that has invaded the lungs. You get rid of this matter when you cough, sneeze, clear your throat or swallow.

The smallest subdivisions of the bronchial tubes are called bronchiolesThe smallest tubes branching off from each bronchus., at the end of which are the air sacs or alveoli.

The alveoliVery small air sacs at the end of each bronchiole. are the very small air sacs that are the destination of air breathed in.

The capillariesVery small blood vessels. are blood vessels that are imbedded in the walls of the alveoli. Blood passes through the capillaries, brought to them by the pulmonary artery and taken away by the pulmonary vein. While in the capillaries, the blood gives off carbon dioxide through the capillary wall into the alveoli and takes up oxygen from the air in the alveoli.

What is Lung Cancer?Top

Lung cancer is a cancer that starts in the lungs. When a person has lung cancer, they have abnormal cells that cluster together to form a tumorA tumor is an abnormal growth of body tissue.. Unlike normal cells, cancer cells grow without order or control and destroy the healthy lung tissue around them. These types of tumors are called malignantA term used to refer to cancerous cells or tumors. Malignant cells are abnormal and grow uncontrollably. They may invade and destroy other parts of the body. tumors.

Why are Malignant Tumors Dangerous?Top

One reason malignant tumors are dangerous is because they grow uncontrollably. When the cancer cells grow too fast, they prevent organs of the body from working well. For example, if cancer affects the lungs, the tumor may grow so large it blocks a major airway so that part of the lung can’t breathe.

Another reason a cancerous tumor is dangerous is because it can spread to different parts of the body. Sometimes a cancerous tumor sheds cells. These cells can be carried to other parts of the body through the blood or the natural fluid around the lung tissue called lymphAn immune system fluid that helps collect unwanted materials for removal from the body.. The cells can begin to grow uncontrollably in the new location and cause problems that keep that part of the body from working properly.

Sometimes other types of cancer can spread to the lungs. This type of tumor is not lung cancer. The information here is about cells in the lung tissue that are abnormal and only become lung cancer.

What are the Types of Lung Cancer?Top

There are two main types of lung cancer: small cell lung cancer (SCLC)About 10% to 15% of all lung cancers are small cell lung cancer (SCLC), named for the small cells that make up these cancers. SCLC often starts in the bronchi near the center of the chest, and it tends to spread widely through the body early in the course of the disease. and non-small cell lung cancer (NSCLC)About 85% to 90% of lung cancers are non-small cell lung cancer (NSCLC). There are three main subtypes of NSCLC, which look different under a microscope but are treated similarly.. Non-small cell lung cancer is more common. It makes up about 80 percent of lung cancer cases. This type of cancer usually grows and spreads to other parts of the body more slowly than small cell lung cancer does. There are three different types of non-small cell lung cancer: adenocarcinomaA form of non-small cell lung cancer often found in an outer area of the lung. It develops in the cells of epithelial tissues, which line the cavities and surfaces of the body and form glands., squamous cell carcinomaA form of non-small cell lung cancer usually found in the center of the lung next to an air tube (bronchus). and large cell carcinomaA form of non-small cell lung cancer that can occur in any part of the lung and tends to grow and spread faster than adenocarcinoma or squamous cell carcinoma.. Each type is different, but they are grouped together because they are treated similarly. There are two different types of small cell lung cancer: small cell carcinoma (oat cell cancer) and mixed small cell/large cell cancer or combined small cell lung cancer. The types of small cell lung cancer are named for the kinds of cells found in the cancer and how the cells look when viewed under a microscope. Small cell lung cancer is almost always associated with cigarette smoking. It is important to know the type of lung cancer you have because it helps determine what treatment options are available.

Types of Lung Cancer Chart Small Cell Non-Small Cell Small Cell Carcinoma Combined Small Cell Carnioma or Mixed Non-Small Cell Carcinoma Adenocarcinoma Squamous Cell Carcinoma Large Cell Carcinoma

Why is Lung Cancer So Serious?Top

One reason lung cancer is so deadly is that it is hard to find in its early stages. It may take years for the lung cancer to grow. Early on there are usually no symptoms. By the time the patient starts to notice symptoms, the cancer has often spread to other parts of the body. Researchers are working hard to develop tests that can find lung cancer in its early stages. Lung cancer can be treated more successfully when it is found early. Researchers are also studying new treatments to help people live longer with lung cancer and even cure lung cancer.

What Causes Lung Cancer?Top

Lung cell mutationAnyone can get lung cancer. Lung cancer happens when cells in the lung mutate or change. Various factors can cause this mutationA permanent change in the DNA sequence of a gene. to happen. Most often, this change in lung cells happens when people breathe in dangerous, toxic substances. Even if you were exposed to these substances many years ago, you are still at risk for lung cancer. Talk to your doctor if you have ever been exposed to any of the substances listed below.

  • Smoking
    Smoking is the number one cause of lung cancer. It causes about 87 percent of lung cancer cases. Tobacco smoke contains many chemicals that are known to cause cancer. Smokers are not the only ones affected by cigarette smoke. Nonsmokers can breathe in secondhand smoke and get lung cancer or other illnesses. Learn how you can quit smoking.
  • Radon
    Radon exposure is the second leading cause of lung cancer. Radon is a colorless, odorless radioactive gas that occurs naturally in soil. It comes up through the soil and enters buildings through small gaps and cracks. One out of every 15 homes in the U.S. has a radon problem. Exposure to radon combined with smoking seriously increases your risk of lung cancer.
  • Hazardous Chemicals
    Hazardous exposure to certain hazardous chemicals poses a lung cancer risk. Working with materials such as asbestos, uranium, arsenic, cadmium, chromium, nickel and some petroleum products is especially dangerous. If you think you may be breathing in hazardous chemicals at your job, talk to your employer and your doctor to find out how you can protect yourself.
  • Particle Pollution
    Particle pollution refers to a mix of very tiny solid and liquid particles that are in the air we breathe. Evidence shows that particle pollution—like that coming from that exhaust smoke—can increase the risk of lung cancer.
  • Genes
    Genetic factors also play a role in the chance that someone gets lung cancer. Mutations in several genes have been linked to lung cancer. This suggests lung cancer has a genetic component. A family history of lung cancer may mean you are at a higher risk of getting the disease.

Not all lung cancer is caused by smoking and these other known risks. For some, the reason is never identified. Continued work to prevent lung cancer and research to improve diagnosis and treatment is critical.


Current Lung Cancer Statistics are Alarming…

Lung cancer is common

  • Lung cancer causes the most cancer deaths worldwide, accounting for 1.3 million deaths annually.1
  • Approximately 373,489 Americans are living with lung cancer.2

Lung cancer is deadly

  • Lung cancer is the leading cancer killer in both men and women in the United States.1
  • Over half of people with lung cancer die within one year of being diagnosed.3
  • In 1987, it surpassed breast cancer to become the leading cause of cancer deaths in women.4
  • Lung cancer causes more deaths than the next three most common cancers combined (colon, breast and prostate).4
  • An estimated 160,340 Americans are expected to die from lung cancer in 2012, accounting for approximately 28 percent of all cancer deaths.4

Lung cancer is costly

  • The National Institutes of Health estimate that cancers cost the United States an overall $264 billion in 2010.5
  • It is estimated that approximately $10.3 billion per year is spent in the United States on lung cancer treatment alone.6

Lung cancer isn’t going away

  • The American Cancer Society estimates that there will be 226,160 new cases of lung cancer in 2012.4
  • These new cases will account for almost 14 percent of all cancer diagnoses.4
  • The number of deaths due to lung cancer has increased approximately 4.3 percent between 1999 and 2008 from 152,156 to 158,656. The number of deaths among men has reached a plateau but the number is still rising among women. In 2006, there were 88,586 deaths due to lung cancer in men and 70,070 in women.7

For more lung cancer statistics see our Lung Cancer Fact Sheet.

Everyone should be concerned about lung cancer.
Preventing and curing lung cancer should be a top priority.


  1. World Health Organization. Cancer. Fact Sheet No 297. February 2009. Accessed on November 17, 2009
  2. U.S. National Institutes of Health. National Cancer Institute: SEER Cancer Statistics Review, 1973-2008.
  3. U.S. National Institutes of Health. National Cancer Institute: SEER Cancer Statistics Review, 1973-2008.
  4. American Cancer Society. Cancer Facts and Figures, 2012.
  5. Centers for Disease Control and Prevention. National Center for Chronic Disease Prevention and Health Promotion. Chronic Diseases at a Glance Reports: Addressing the Cancer Burden, 2011.
  6. U.S. National Institutes of Health. National Cancer Institute. A Snapshot of Lung Cancer. October 2011
  7. Centers for Disease Control and Prevention. National Center for Health Statistics. National Vital Statistics Report. Deaths: Final Data for 2008. December 2011; 59(10).

Early detection of lung cancer can increase survival rates. Call the Lung Helpline at 1-800-LUNGUSA or talk to your doctor about lung cancer screening.