Gaseous exchange is the movement of oxygen into the body and the expelling of carbon dioxide out of the body. This is facilitated by diffusion through the alveolar surface within the lungs. There are about 300 million alveoli in each lung which gives a substantial surface area for exchange to transpire over.
The surface of the alveoli is very thin and moist so enabling the gases to pass through or exchange quickly. Situated within the walls of each alveoli lies a network of capillaries. Oxygen gets passed from the alveoli into bloodstream, which is then used up by cells within the body where it is used for respiration. The blood then carries back the waste which is carbon dioxide back through the alveoli walls where it is breathed out as you exhale.
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