Answer:
body cells, capillaries, alveoli
Step-by-step explanation:
Respiration occurs at cellular level in the organisms. Once carbon dioxide is produced in the cells after completion of cellular respiration, it readily enters very thin blood vessels named as capillaries. The reason why carbon dioxide readily enters capillaries is gradient of partial pressure of carbon dioxide between our cells and blood of capillaries. Due to the consistent generation of carbon dioxide in the cells as a result of respiration, its partial pressure is much more inside the cell as compared to the capillaries that is why it enters the capillaries readily through simple diffusion. Due to the presence of large amount of this carbon dioxide, the blood in the capillaries is termed as deoxygenated blood. Finally this deoxygenated blood is transported to the alveoli which are small balloon like structures situated in our lungs and from alveoli this carbon dioxide is exhaled back to the environment.