What is Breathing?
'''Breathing''' is moving [[air]] in and out of the [[lung]]s. The air going in and out is called ''breath''. If a person cannot breathe, they will die. [[File:Gas exchange in the aveolus simple (en).svg|350px|thumb|Gas exchange in humans. Oxygen and carbon dioxide switch places between a [[capillary]] (part of the bloodstream) and an [[alveolus]] (an air sac in the lungs).]] Breathing helps people do two very important things:<ref name=Ganong>{{cite book |author=Barrett, Kim E.; Barman, Susan M. | display-authors = etal |date=April 26, 2012 |title=Ganong's Review of Medical Physiology |url= |location= |publisher=McGraw-Hill Education |page= |edition=24th |isbn=978-0071780032}}</ref><ref name=gas>{{cite web |url=http://www.merckmanuals.com/home/lung-and-airway-disorders/biology-of-the-lungs-and-airways/exchanging-oxygen-and-carbon-dioxide |title=Exchanging Oxygen and Carbon Dioxide |last1=Lechtzin, MD, MHS |first1=Noah|website=Merck Manual |publisher=Merck & Co., Inc. |accessdate=January 29, 2016 |quote=}}</ref> # Get [[oxygen]] into the body. Every part of the body needs oxygen to survive. The only way humans can get oxygen is to [[Inhalation|breathe it in]]. # Get [[carbon dioxide]] (CO<sub>2</sub>) out of the body. When the [[Aerobic respiration|body makes energy]], carbon dioxide gets left over. The body needs to get rid of extra carbon dioxide, because too much of it is [[poison]]ous. The only way humans can get rid of carbon dioxide is to breathe it out. When a person breathes in, they bring air into their lungs. Air has oxygen in it. The oxygen goes from the lungs into the person's [[bloodstream]]. When oxygen goes into the bloodstream, extra carbon dioxide comes out and goes into the lungs. This is called [[Exchange of gases|gas exchange]]: basically, oxygen and carbon dioxide are changing places. Oxygen is now in the bloodstream, which can carry that oxygen around to every part of the body. Also, carbon dioxide is now in the lungs, where it can be breathed out.<ref name=gas /> Adults brea