MedlinePlus Medical Encyclopedia: Breathing

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Breathing

Breathing consists of two phases. The first phase is the inspiration phase. Inspiration allows air to flow into the lungs. The second phase is expiration. Expiration involves gases leaving the lungs. During inspiration, the diaphragm and intercostal muscles contract allowing air to enter the lungs. During expiration, the inspiration muscles relax forcing gases to flow out of the lungs.

Update Date: 1/18/2007

Updated by: Benjamin W. Van Voorhees, MD, MPH, Assistant Professor of Medicine and Pediatrics, The University of Chicago, Chicago, IL. Review provided by VeriMed Healthcare Network.

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