Define breathing explain the mechanism of breathing in human being
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Answer:
Breathing can be defined as the process of intake of air from the mouth and nostrils called as inhalation and then passing out of the air from the nose called as exhalation. The mechanism of breathing is simple, it involves no chemical reaction.
Breathing in humans involves the air enters in the body, through the nostrils, then to the nasal passage to larynx, then trachea and finally inside the lungs where exchange of gases takes place. Inside the lungs there are various tubes called as bronchi, alveoli and capillaries. Inside the capillaries the oxygenated blood gets displaced with the deoxygenated blood. Through blood oxygen reaches to all the body parts and the carbon dioxide is exhaled out by following the same path through which the oxygenated air enters the body through nostrils in reverse order.
The breathing mechanism of a human being is described as a pressure gradient driven mechanism. The "difference in pressure" between the "atmosphere" and the internal human body helps in the "exchange of gases".
The "intercostal muscles" and the "diaphragm" line the thoracic cavity.
When the "volume of the thoracic cavity" decreases, due to the relaxation of the intercostal muscles. This increases the pressure within the cavity causing expulsion of CO2 rich air.
When the intercostal muscles expand the volume of the thoracic cavity increases causing pressure decrease in the thoracic cavity causing an intake of O2 air from the atmosphere.