One is that when we are bored or tired, wejust don't breathe as deeply as we usually do. As this theory goes, our bodies take in less oxygen because our breathing has slowed. Therefore, yawning helps us bring more oxygen into the blood and move more carbondioxide out of the blood.
it is copied one from internet
Hey!!! THis is not right
soory your answer is also right
  • Brainly User
Question=Why do we yawn?
Answer=When we are tired,our lungs and the rest of the respiratory system slows down until there is too little air in our lungs.Our body then sets off a spasm (a quick movement) in the muscles of our mouth.throat and chest.This forces us to take a deep breath of air (yawn) to take in more air.


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