What Breathing Does for the Body - How the Lungs Work - What Breathing Does for the Body

Breathing involves two phases: breathing in and breathing out. Your lungs deliver oxygen and remove carbon dioxide from your blood in a process called gas exchange. Gas exchange happens in the capillaries surrounding the alveoli, where the oxygen that is breathed in enters the circulatory system and carbon dioxide in the blood is released to the lungs and then breathed out. If you have problems breathing, gas exchange may be impaired, increasing the risk of serious health problems.

Breathing in
- How the Lungs Work - What Breathing Does for the Body

When you breathe in, or inhale, your diaphragm contracts and moves downward. This increases the space in your chest cavity, and your lungs expand into it. The muscles between your ribs also help enlarge the chest cavity. They contract to pull your rib cage both upward and outward when you inhale.

As your lungs expand, air is sucked in through your nose or mouth. The air travels down your windpipe and into your lungs. After passing through your bronchial tubes, the air travels to the alveoli, or air sacs.

Gas exchange
- How the Lungs Work - What Breathing Does for the Body

Gas exchange in your lungs. When you breathe in, air enters your nose or mouth, and passes into your windpipe, also called the trachea. At the bottom, the windpipe divides into two bronchial tubes, then branches into smaller bronchioles. The brochioles end in tiny air sacs, called alveoli. Here the oxygen you inhaledi passes into the bloodstream, and carbon dioxide from your body passes out of the bloodstream. The carbon dioxide is expelled from your body when you exhale. Medical Animation Copyright © 2019 Nucleus Medical Media Inc. All rights reserved.

Through the very thin walls of the alveoli, oxygen from the air passes into your blood in the surrounding capillaries. At the same time, carbon dioxide moves from the capillaries into the air sacs. This process of exchanging oxygen for carbon dioxide is called gas exchange. The oxygen in your blood is stored inside your red blood cells by a protein called hemoglobin.

The oxygen-rich blood from the lungs is carried to the left side of the heart through the pulmonary veins. The left side of the heart pumps the blood to the rest of the body. There, the oxygen in the red blood cells moves from blood vessels into surrounding tissues.

As carbon dioxide is released from the cells of the body, it travels in the bloodstream to the heart. The blood rich in carbon dioxide is then pumped from the right side of the heart through the pulmonary artery to the lungs, where gas exchange occurs.

For more information on blood flow, visit our How the Heart Works Health Topic.

Breathing out
- How the Lungs Work - What Breathing Does for the Body

When you breathe out, or exhale, your diaphragm and rib muscles relax,reducing the space in the chest cavity. As the chest cavity gets smaller, your lungs deflate, similar to the releasing of air from a balloon. At the same time, carbon dioxide-rich air flows out of your lungs through the windpipe and then out of your nose or mouth.

Breathing out requires no effort from your body unless you have a lung disease or are doing physical activity. When you are physically active, your abdominal muscles contract and push your diaphragm against your lungs even more than usual. This rapidly pushes air out of your lungs.

Conditions that affect the respiratory system
- How the Lungs Work - What Breathing Does for the Body

Damage, infection, or inflammation in the lungs or airways or both can lead to the following conditions.

Exposure to cigarette smoke, air pollutants, or other substances can damage the airways, causing disease of the airways or making a disease more severe.