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In order for the lungs to expel air the diaphragm relaxes, which pushes up on the lungs. The air then flows through the trachea then through the larynx and pharynx to the nasal cavity and oral cavity where it is expelled out of the body. [2] Exhalation takes longer than inhalation and it is believed to facilitate better exchange of gases.
Real-time magnetic resonance imaging of the human thorax during breathing X-ray video of a female American alligator while breathing. Breathing (spiration [1] or ventilation) is the rhythmical process of moving air into and out of the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxygen.
The lungs expand and contract during the breathing cycle, drawing air in and out of the lungs. The volume of air moved in or out of the lungs under normal resting circumstances (the resting tidal volume of about 500 ml), and volumes moved during maximally forced inhalation and maximally forced exhalation are measured in humans by spirometry. [12]
In the lungs, oxygen from the inhaled air is transferred into the blood and circulated throughout the body. Carbon dioxide (CO 2) is transferred from returning blood back into gaseous form in the lungs and exhaled through the lower respiratory tract and then the upper, to complete the process of breathing.
Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions in some disease states) and does not need conscious control or effort. However, breathing can be consciously controlled or interrupted (within limits).
The process of breathing does not fill the alveoli with atmospheric air during each inhalation (about 350 ml per breath), but the inhaled air is carefully diluted and thoroughly mixed with a large volume of gas (about 2.5 liters in adult humans) known as the functional residual capacity which remains in the lungs after each exhalation, and ...
This cycle, which is controlled by the autonomic nervous system, has a mean duration of two and a half hours but varies widely with age, body-posture, and other conditions. [5] He further observed and documented that the turbinates in the dependent nasal fossa fill when the patient is lying down. The nasal cycle is an alternation in both time ...
At the other end is an orifice through which such gases are directed into the lungs and may also include a balloon (referred to as a cuff). The tip of the endotracheal tube is positioned above the carina (before the trachea divides to each lung) and sealed within the trachea so that the lungs can be ventilated equally. [25]