The lungs are an essential part of the respiratory system. The respiratory system facilitates breathing and has two parts: the upper respiratory tract, which includes the airways like the nose, mouth, sinuses, and windpipe (trachea), and the lower respiratory tract, which consists of the lungs and bronchial tubes. 

The lungs’ main role is to deliver oxygen to the blood and remove carbon dioxide from the blood. Air enters the nose or mouth and passes through your windpipe and into the bronchial tubes when you breathe in. The bronchial tubes lead into the lungs and branch out into smaller tubes known as bronchioles, which end in small air sacs known as alveoli.

The alveoli are surrounded by capillaries (small blood vessels) that carry oxygen-low blood through them. Oxygen from the air in the alveoli flows into the blood, and carbon dioxide moves out of the blood and into the alveoli.

The carbon dioxide flows from the alveoli and back up through the respiratory system, where it is exhaled out of the mouth or nose.

In this article, you will learn about lung anatomy, how lungs function, and how to keep them healthy.

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Lung Anatomy

Though both lungs are similar in makeup, they are asymmetrical. The left lung is slightly smaller than the right lung to accommodate the heart. The right lung has three lobes—the right upper lobe, the right middle lobe, and the right lower lobe. The left lung has an upper and lower lobe.

The lungs are wrapped in pleura, a two-layer membrane. Fluid between the layers helps reduce friction when breathing.

Both lungs have a pulmonary artery, bronchial arteries, and pulmonary veins that carry blood in and out of the lungs.

The alveoli inside the lungs are small thin sacs that allow for an exchange of gases, bringing oxygen into the blood and carbon dioxide out of the blood.

Muscles around the lungs aid in breathing. These muscles include the diaphragm, a disk-shaped muscle that sits under the lungs, and the intercostal muscles that run between the ribs. Muscles in the neck and mouth also help with breathing.

Lung Function

Though it is possible to control your breathing—you can take a deep breath, a shallow breath, or even hold your breath for a short period—most breathing happens without thought.

The autonomic nervous system controls breath and works involuntarily. The system senses when you need more oxygen, such as when exercising, and makes adjustments.

The autonomic nervous system has two divisions that have different functions in breathing, which are:

  • The parasympathetic system narrows the bronchial tubes and widens the pulmonary blood vessels.
  • The sympathetic system widens the bronchial tubes to allow more air in and narrows the pulmonary blood vessels. 

To help these systems, there are various sensors throughout the body to signal the body to adjust breathing rate:

  • Sensors in the joints and muscles detect movement, which can signal to the body that you are exercising and an increase in breathing rate is necessary.
  • Sensors in the brain and blood vessels measure oxygen and carbon dioxide levels in the blood, which signals the type of breathing rate adjustment needed.
  • Sensors in the airways themselves can detect substances that may irritate the lungs, such as smoke or allergens, which may cause coughing or sneezing.

Lung Function Tests

A lung function test can determine the health of the lungs. These tests show how well the lungs work and can include:

  • Spirometry: Spirometry is the most common lung function test. The test consists of breathing in and blowing into a tube that records the volume of air inhaled and exhaled. A healthcare provider walks you through the test and has you inhale and exhale in different manners—sometimes forcefully and others at a normal rate.
  • Diffusion capacity test: During this test, a gas mixture is inhaled and then exhaled to determine how well the alveoli function at moving gases into and out of the lungs and blood.
  • Overnight pulse oximetry (OPO): Overnight pulse oximetry can detect the amount of oxygen in the blood over an extended period, mainly at night during sleep. A sensor is placed over the tip of your finger during the test, and the oxygen saturation levels (the amount of oxygen in the blood) are recorded.
  • Six-minute walk test: This test can measure how well your heart and lungs work during exercise or movement. You will walk for six minutes during the test while your heart rate, oxygen levels, and blood pressure are measured.

Respiratory Diseases Affecting the Lungs

There are various respiratory diseases that can affect the lungs and reduce their ability to function. These diseases include:

  • Asthma: Asthma can obstruct the airways, causing wheezing or difficulty breathing. While the cause of asthma is not fully understood, certain pollutants can make it worse such as tobacco smoke and air pollution.
  • Chronic obstructive pulmonary disease (COPD): "COPD" is a term used to describe a group of progressive diseases that causes damage to the tissues of the lungs. This results in a variety of symptoms from shortness of breath to chest pain, a chronic cough, and tiredness.
  • Cystic fibrosis (CF). Cystic fibrosis is a genetic condition that causes the mucus in the lungs to become sticky and disrupt normal breathing patterns.
  • Lung cancer: Cancer of the lungs is a major cause of cancer-related deaths. Cancer of the lungs can affect any part of the lung structures.
  • Pneumonia: Pneumonia is often caused by infection. It results in inflammation in the alveoli of the lungs and can cause difficulty breathing. 
  • Tuberculosis: Tuberculosis is a highly contagious bacterial infection that can damage the lungs if not treated.

Maintaining Lung Health

Taking good care of your overall health, such as by doing the following, can help maintain lung health as well:

  • Regular exercise can keep your lungs healthy and strong.
  • Seeing your healthcare provider regularly for checkups can help detect problems with the lungs early, even if you have no symptoms.
  • Quitting smoking can prevent many lung issues since smoking is the leading cause of lung cancer and COPD issues like emphysema.
  • Taking good care of yourself to minimize exposure to infections can also help prevent lung issues, including washing your hands often, getting recommended vaccinations, and avoiding being around others who are sick.
  • Avoid air pollutants by paying attention to the air quality in your area and staying indoors when air quality is bad, avoiding secondhand smoke, and limiting your exposure to chemicals in your house and at work.


The lungs play an important part in the respiratory system. Their main function is to provide oxygen to the blood and remove carbon dioxide from the blood. Various diseases can affect the lungs, including asthma, infections, COPD, and cancer. Keep the lungs healthy by avoiding pollutants, getting regular exercise, and ceasing smoking.

A Word From Verywell

The lungs are a vital part of your health. When they are working as they should they will provide the oxygen you need to enjoy life with energy and vigor. If you have difficulty breathing or any symptoms related to lung disease, it’s important to talk to your healthcare provider right away.

Frequently Asked Questions

  • What are the first signs of lung problems?

    Some of the first signs of lung problems are shortness of breath, difficulty breathing, and tiredness.

  • What role do the lungs play in the respiratory system?

    The lungs provide oxygen to the blood and remove carbon dioxide from the blood.

  • How can you take care of your lungs?

    Taking care of your overall health can help you take care of your lungs. Exercise regularly, get routine checkups and avoid inhaling pollutants that can damage your lungs.

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