Blood is the river of life that flows through the human body. We cannot live without it. The heart pumps blood to all our body cells, supplying them with oxygen and food. At the same time, blood carries carbon dioxide and other waste products from the cells. Blood also fights infection, keeps our temperature steady, and carries chemicals that regulate many body functions. Finally, blood even has substances that plug broken blood vessels and so prevent us from bleeding to death.
When oxygen combines with certain cells
