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The oxygen enters the respiratory system through inhalation and then it enters the blood stream to be circulated throughout the body while carbon dioxide from the tissues enter the blood, then to the lungs where it is exhaled..

That's my answer :)))

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You breathe then the oxygen from the plants then goes through your nose then to the lungs then releasing some air which is called carbon dioxide and it exits out through our nose. The blood goes to the heart, pumping blood to every nerves and organs so we can survive then it returns over and over again. :)
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