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Definition of RESPIRATION
a: the placing of air or dissolved gases in intimate contact with the circulating medium of a multicellular organism (as by breathing)
b: a single complete act of breathing
: the physical and chemical processes by which an organism supplies its cells and tissues with the oxygen needed for metabolism and relieves them of the carbon dioxide formed in energy-producing reactions
: any of various energy-yielding oxidative reactions in living matter
a: the movement of respiratory gases (as oxygen and carbon dioxide) into and out of the lungs b: a single complete act of breathing <30 respirations per minute>
: the physical and chemical processes (as breathing and diffusion) by which an organism supplies its cells and tissues with the oxygen needed for metabolism and relieves them of the carbon dioxide formed in energy-producing reactions
Process of taking in air for oxygen and releasing it to dispose of carbon dioxide. The amount of air inhaled and exhaled in an average human breath (tidal volume) is about one-eighth the amount that can be inhaled after exhaling as much as possible (vital capacity). Nerve centres in the brain regulate the movements of muscles of respiration (diaphragm and chest wall muscles). Blood in the pulmonary circulation brings carbon dioxide from the tissues to be exhaled and takes up oxygen from the air in the pulmonary alveoli to carry it to the heart and the rest of the body. Because the body stores almost no oxygen, interruption of respirationby asphyxiation, drowning, or chest muscle paralysisfor more than a few minutes can cause death. Disorders affecting respiration include allergy, asthma, bronchitis, emphysema, pneumonia, and tuberculosis. See alsorespiratory system; respiratory therapy.