How the Lungs and Respiratory System Work

You usually don't even notice it, but twelve to twenty times per minute, day after day, you breathe -- thanks to your body's respiratory system. Your lungs expand and contract, supplying life-sustaining oxygen to your body and removing from it, a waste product called carbon dioxide.

The Act of Breathing

Breathing starts at the nose and mouth. You inhale air into your nose or mouth, and it travels down the back of your throat and into your windpipe, or trachea. Your trachea then divides into air passages called bronchial tubes.

For your lungs to perform their best, these airways need to be open during inhalation and exhalation and free from inflammation or swelling and excess or abnormal amounts of mucus.

      As the bronchial tubes pass through the lungs, they divide into smaller air passages called bronchioles. The bronchioles end in tiny balloon-like air sacs called alveoli. Your body has over 300 million alveo

The alveoli are surrounded by a mesh of tiny blood vessels called capillaries. Oxygen from the inhaled air passes through the alveoli walls and into the blood.

After absorbing oxygen, the blood leaves the lungs and is carried to your heart. Your heart then pumps it through your body to provide oxygen to the cells of your tissues and organs.

As the cells use the oxygen, carbon dioxide is produced and absorbed into the blood. Your blood then carries the carbon dioxide back to your lungs through the capillaries, where it is removed from the body when you exhale.

The Diaphragm's Role in Breathing

Inhalation and exhalation are the processes by which the body brings in oxygen and expels carbon dioxide. The breathing process is aided by a large dome-shaped muscle under the lungs called the diaphragm.

When you breathe in, the diaphragm contracts, creating a vacuum that causes a rush of fresh air into the lungs.

The opposite occurs with exhalation, where the diaphragm relaxes and the lungs deflate.

Clearing the Air

The respiratory system has built-in methods to prevent harmful substances in the air from entering the lungs.

      Small hairs in your nose, called cilia, help filter out large particles. Cilia are also found along your air passages and move in a sweeping motion to keep the air passages clean. But if harmful substances, such as cigarette smoke, are inhaled, the cilia stop functioning properly, causing health problems like bronchitis.

Mucus produced by cells in the trachea and bronchial tubes keeps air passages moist and aids in stopping dust, bacteria and viruses, allergy-causing substances, and other substances from entering the lungs.

Impurities that do reach the deeper parts of the lungs can be moved up via mucous and coughed out or swallowed.

Reviewed by the doctors at The Cleveland Clinic Department of Pulmonary, Allergy and Critical Care Medicine.