The red blood cells carry oxygen from the lungs to the different parts of the body. One trip takes the cell from the heart through the various blood vessels to the different parts of the body and back to the heart in 20 seconds. A red blood cell is estimated to live in the body for four months. They originate in the bone marrow and during their lifetime, they make 250,000 trips circumnavigating the body before returning to the bone marrow where they eventually die.
