A student was talking with her younger brother about what she was learning. She asked him if he knew how food and oxygen got to the cells in the body. He responded,
Sure, I know. This is how it works: We eat food, and it goes through food tubes to the cells. We breathe in air, and it goes through air tubes to the cells in the body.
Build on the younger brother’s ideas to provide a more scientific description of what happens when food and oxygen enter the body and travel to cells.