Lungs & Respiratory System Basics
Each day we breathe about 20,000 times. All of this breathing couldn't happen without help from the respiratory system, which includes the nose, throat, voice box, windpipe, and lungs. With each breath, you take in air through your nostrils and mouth, and your lungs fill up and empty out. As air is inhaled, the mucous membranes of the nose and mouth warm and humidify the air.

Although we can't see it, the air we breathe is made up of several gases. Oxygen is the most important for keeping us alive because body cells need it for energy and growth. Without oxygen, the body's cells would die.

Carbon dioxide is the waste gas that is produced when carbon is combined with oxygen as part of the body's energy-making processes. The lungs and respiratory system allow oxygen in the air to be taken into the body, while also enabling the body to get rid of carbon dioxide in the air breathed out.

Respiration is the term for the exchange of oxygen from the environment for carbon dioxide from the body's cells. The process of taking air into the lungs is called inhalation or inspiration, and the process of breathing it out is called exhalation or expiration.

Even if the air you breathe is dirty or polluted, your respiratory system filters out foreign matter and organisms that enter through the nose and mouth. Pollutants are breathed or coughed out, destroyed by digestive juices, or eaten by macrophages, a type of blood cell that patrols the body looking for germs to destroy.

Tiny hairs called cilia (pronounced: SIL-ee-uh) protect the nasal passageways and other parts of the respiratory tract, filtering out dust and other particles that enter the nose with the breathed air. As air is inhaled, the cilia move back and forth, pushing any foreign matter (like dust) either toward the nostrils, where it is blown out, or toward the pharynx, where it travels through the digestive system and out with the rest of the body's waste.