Espa?ol
PDFs by language
Our 24/7 cancer helpline provides information and answers for people dealing with cancer. We can connect you with trained cancer information specialists who will answer questions about a cancer diagnosis and provide guidance and a compassionate ear.
Chat live online
Select the Live Chat button at the bottom of the page
Call us at 1-800-227-2345
Available any time of day or night
Our highly trained specialists are available 24/7 via phone and on weekdays can assist through online chat. We connect patients, caregivers, and family members with essential services and resources at every step of their cancer journey. Ask us how you can get involved and support the fight against cancer. Some of the topics we can assist with include:
For medical questions, we encourage you to review our information with your doctor.
The respiratory system is made up of structures and organs that aid in breathing.
The organs of the respiratory system include the:
Your lungs are 2 sponge-like organs in your chest. Your right lung has 3 sections, called lobes. Your left lung has 2 lobes. The left lung is smaller because the heart takes up more room on that side of the body.
A thin lining layer called the pleura surrounds the lungs. The pleura protects your lungs and helps them slide back and forth against the chest wall as they expand and contract during breathing.
Below the lungs, a thin, dome-shaped muscle called the diaphragm separates the chest from the abdomen.
When you breathe in, air enters through your mouth or nose and goes into your lungs through the trachea (windpipe). The trachea divides into tubes called bronchi, which enter the lungs and divide into smaller bronchi. These divide to form smaller branches called bronchioles. At the end of the bronchioles are tiny air sacs known as alveoli.
Alveoli are located at the end of the smallest bronchioles, known as respiratory bronchioles. The alveoli are tiny air-filled pockets located in the lungs at the end of the bronchi. They cluster together in groups of 20 to 30. One group of alveoli is called an alveolar sac.
Together with small blood vessels called capillaries, alveoli are responsible for gas exchange during breathing. Oxygen is inhaled into the lungs and carbon dioxide is exhaled during this gas exchange.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.
Last Revised: December 13, 2022
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
Sign up to stay up-to-date with news, valuable information, and ways to get involved with the American Cancer Society.
If this was helpful, donate to help fund patient support services, research, and cancer content updates.