You live because you breathe. Inhaled breath brings life-sustaining oxygen into your body. Oxygen is the fuel that makes your body function. Every minute you breathe in about 13 pints of air. Your lungs are essentially 1500 miles of airways, through which oxygen is delivered to all parts of the body from the lungs, and carbon dioxide exhaled from the lungs is sent out into the atmosphere.

Air has a long journey to the lungs – past the windpipe, the vocal cords, to the lower ribs that meet in the center of your chest. From there, the windpipe branches off into the left lung and the right lung. Inside the lung, bronchi connect with tiny air sacs called alveoli. If spread out flat, all the air sacs in your lungs would cover about a third of a regulation tennis court.

Inhaled oxygen goes into the alveoli, through the lung’s capillaries and into the body’s arteries for delivering oxygen to all parts of the body. On the way, the carbon dioxide-filled blood releases into the alveoli and begins the journey back through your chest cavity, larynx, diaphragm, trachea, nose and mouth, and out into the air.

When your body’s diaphragm contracts, oxygen is pulled in; when your diaphragm contracts, carbon dioxide is released from your lungs. The red blood cells are the conductors of this air exchange. Breathing is automatic for this highly intricate system.

A description of the respiratory system’s structures follows:

Sinuses: Hollow spaces in the bones of your head, that connects to your nose. Regulates temperature and humidity of air breathed in, and gives "sound" to your voice.

Nose: Outside air comes in through the nose. Small hairs clean the air that comes in.

Mouth: Air can also enter by this route.

Adenoids: Lymph tissue at the top of the throat. Helps to resist infection and producing cells to fight infection.

Tonsils: Lymph nodes in the wall of the throat. Part of the body’s germ fighters.

Throat: Collects incoming air from the nose and mouth and passes in down the windpipe, or trachea.

Epiglottis: Tissue gap that guards the windpipe, and closes when anything is swallowed.

Voice Box: Also called the larynx that houses the vocal cords. Moving air breathed in and out creates our "voice."

Esophagus: Passage that leads from the mouth and throat to the stomach.

Windpipe: Passage leading from the throat to the lungs.

Lymph Nodes: Found against the walls of the bronchial tubes and windpipe.

Ribs: Support and protect the chest cavity and help lungs contract and expand.

Bronchial tubes: One branches off to each lung.

Lobes: Each lung is divided into lobes. Each lobe acts like a balloon with sponge-like tissue. The right lung has three lobes; the left lung, two lobes.

Pleura: Membranes that surround each lobe of the lungs and separate the lungs from the chest wall.

Cilia: Line the bronchial tubes in a wave-like motion that carries mucus upward and out into the throat where it’s either coughed out or swallowed. Mucus catches dust germs and other matter that comes into your lungs. You rid your lungs of mucus when you cough, sneeze, clear your throat or swallow.

Diaphragm: Strong wall of muscle that separate the chest cavity from the abdominal cavity. As it moves downward, it creates suction to draw air in and expand the lungs.

Bronchioles: Smallest subdivisions of the bronchial tubes. At the end are air sacs, or alveoli, that are the final destination of air breathed in. Blood passes through the capillaries in the alveoli, brought by the pulmonary artery, and taken away by the pulmonary vein.