Respiration is defined as the movement of oxygen from the outside environment to the cells within tissues, and the transport of carbon dioxide in the opposite direction. Respiration is the biochemical process in which the cells of an organism obtain energy by combining oxygen and glucose, resulting in the release of carbon dioxide, water, and ATP (the currency of energy in cells).

The primary organs of the respiratory system are the lungs, which function to take in oxygen and expel carbon dioxide as we breathe.

The gas exchange process is performed by the lungs and respiratory system. Air, a mix of oxygen and other gases, is inhaled.

In the throat, the trachea, or windpipe, filters the air. The trachea branches into two bronchi, tubes that lead to the lungs.

Once in the lungs, oxygen is moved into the bloodstream. Blood carries the oxygen through the body to where it is needed.

Red blood cells collect carbon dioxide from the body’s cells and transport it back to the lungs.

An exchange of oxygen and carbon dioxide takes place in the alveoli, small structures within the lungs. The carbon dioxide, a waste gas, is exhaled and the cycle begins again with the next breath.

The diaphragm is a dome-shaped muscle below the lungs that controls breathing. The diaphragm flattens out and pulls forward, drawing air into the lungs for inhalation. During exhalation the diaphragm expands to force air out of the lungs.