Action of taking air into the lungs and then letting it out, a process normally done without thinking and controlled by the autonomic nervous system.
The process of taking air into the lungs and letting it out again. In breathing, air is inhaled into the lungs through the nose or mouth as a result of muscle contractions, and it is exhaled as a result of muscle relaxation.
The alternation of active inhalation (or inspiration) of air into the lungs through the mouth or nose with the passive exhalation (or expiration) of the air. During inhalation the diaphragm and intercostal muscles contract, which enlarges the chest cavity and draws air into the lungs. Relaxation of these muscles forces air out of the lungs at exhalation. Breathing is part of respiration and is sometimes called external respiration. There are many types of breathing in which the rhythm, rate, or character is abnormal.
The process of breathing facilitates the exchange of air between the lungs and the bloodstream, enabling the uptake of oxygen and elimination of carbon dioxide. The respiratory center in the brainstem governs the control of breathing. During inhalation, the diaphragm contracts and flattens, while the intercostal muscles located between the ribs contract, lifting and expanding the ribcage. This expansion of the chest cavity increases its volume, causing the lungs to expand, and the resulting decrease in pressure draws air into the lungs. During exhalation, the chest muscles and diaphragm relax, allowing the ribcage to descend, and the lungs contract, expelling air from the respiratory system.
During normal, calm breathing, only a small fraction, less than one-tenth, of the air present in the lungs is exhaled, which is then replaced by an equal amount of fresh air, known as the tidal volume. This newly inhaled air mingles with the stagnant air, termed the residual volume, that remains in the lungs. The average breathing rate for an adult at rest typically ranges from 13 to 17 breaths per minute.
The typical breathing rate is 16 breaths per minute. This frequency can rise during physical activity or in the presence of specific respiratory issues. Conversely, it can drop when the individual is in a coma or under the effects of certain medications.