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Breathing and Gas Exchange
Breathing moves air, while gas exchange and circulation together supply oxygen and remove carbon dioxide.
#Moving air and exchanging gases are linked tasks
NHLBI describes breathing in as bringing air into the lungs and breathing out as removing air. At the lungs, oxygen moves from inhaled air into blood while carbon dioxide moves from blood into the lungs to be exhaled. Gas exchange is the transfer of those gases, rather than simply the movement of air.
Airways, respiratory muscles, blood vessels and nervous control all contribute. The distinction helps explain how breathing connects the environment with the body's internal transport system. It does not allow this page to judge a person's breathing or interpret an oxygen measurement.
Evidence: NHLBI: the lungs
#The airways lead to exchange surfaces
NHLBI follows air through the nose or mouth, windpipe and branching bronchial tubes into smaller bronchioles, which end in clusters of air sacs called alveoli. Capillaries surround these sacs. Oxygen moves from the air in the alveoli into the blood, while carbon dioxide moves in the other direction.
The circulatory system brings blood to and from the lungs and carries oxygen onward to organs and tissues. Air movement and blood flow therefore meet at the exchange surface. This simplified description is not a test of airway function, lung disease or the cause of breathlessness.
Evidence: NHLBI: the respiratory system
#Muscles and nervous signals support breathing
NHLBI identifies the diaphragm as the main breathing muscle and describes how respiratory muscles create the conditions for air to flow into the lungs. As muscles relax during ordinary exhalation, the lungs recoil. Nervous control usually keeps breathing going without conscious attention, while sensors send information to breathing centres in the brain as needs change.
This is a mechanism overview, not a breathing exercise, rehabilitation programme or oxygen-therapy instruction. It provides no target breathing rate or personal advice about changing breathing patterns. Clinical assessment requires more than this general model.
Evidence: NHLBI: breathing muscles and control
Source note
The sections above were checked against the linked sources. No clinical review has been performed. This is general research education, not a clinical guideline.