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Explain the process of inspiration and expiration under normal conditions.

Last updated date: 13th Jul 2024
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Under normal conditions, an adult person respires 15-20 per minute. It is a process in which a person takes in oxygen for the tissues to work properly and gives out carbon dioxide taken from the blood as a waste product. The pure oxygen is transported to the organs through blood with the binding of haemoglobin.

Complete answer:
Respiration process involves taking in oxygen (inspiration) which occurs with the mechanism listed below:
When the oxygen is inhaled from the nasal pore from the surroundings, it moves through the nasal passage – windpipe and reaches to alveoli.
Alveoli are attached to the lungs surface where the gases diffuse into the lungs.
Oxygen is transferred to the lungs when the thoracic cavity expands as a result of the contraction of diaphragm.
This makes external intercostal muscle contract making the ribs move forward or outwards, this results in the decreased internal pressure in lungs and increased thoracic cavity space.
This favours the oxygen to take in the lungs and transfer to the body organs.
In expiration following mechanism occurs :
Carbon dioxide is collected from the body organs and transferred to the lungs so that it can be expelled out from the body.
Lungs diffuse the carbon dioxide inside them and the diaphragm relaxes which result in the relaxation of external intercostal muscles thereby decreasing the thoracic cavity.
The pressure in the lungs is increased.
Due to increased pressure, carbon dioxide is expelled out from the lungs – from alveoli to nasal passage and then to the environment.
This is how one respiration takes place.

Note: Pleural space is present between the inner thoracic wall and the external surface of the lung which is filled with fluid known as pleural fluid. This fluid helps the lungs remain to attach to the place against the thoracic wall by creating surface tension between them.