Grade 7, Science Olympiad (CBSE) - Breathing in human beings 

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Grade 7  |   Science  |   Breathing in human beings, Respiration in plants and animals, Olympiad, CBSE, ICSE, SOF, ITO

Breathing in humans
It the process of inhaling ( taking in) and exhaling (giving out) the oxygen from the air,for the process of respiration to occur.
Rate of breathing
The breathing rate of human beings is 15-18 breaths per minute. This is the normal rate of breathing when we are not involved in any physical work, such as running, swimming, jogging, etc. 
Process of breathing

As the air passes through the tiny hair in the nasal cavity, all the dust particles in the air get stuck on them. Hence, the air which reaches the lungs is being purified while its intake. The air passes through the nasal passage and crosses the pharynx, larynx, and windpipe before reaching finally inside the lungs. There is a mucous lining running from the nasal cavity to the lungs. As we know lungs are the present inside the chest cavity, and there is a large muscular sheet which holds the lungs or acts as the floor for the chest cavity called the diaphragm. It is a membrane which is present between the chest cavity and the abdomen. 
When we inhale, the diaphragm moves down and the ribcage expands with the expansion of the lungs. 

When we exhale, the diaphragm moves up and the rib cage contracts with the contraction of lungs.

The digram below shows the movement of the diaphragm while inhalation and exhalation.


The movement of the diaphragm is controlled by a group of muscles called intercostal muscles.

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