I begin my journey into the bone marrow. Have you ever seen how flexible bone marrow is!?! It's really exciting. I form from a hemocytoblast, which takes about 2 days. The body produces about two million red blood cells every second. So there’s a lot of me to get around. I finally leave and make my way through the capillary veins in the company of my plasma buddy. We take up most of the space because there's so much to do, but speaking for myself, these guys aren't that big to begin with. Finally I turn to what I like to call the capillary veins' big brother the arteries. These are much bigger but they do more work and they are stronger, the capillaries are nowhere near as strong! I'm finally making my way to your heart! If you make a fist, that's about the average size of your heart. The heart pumps about 2,000 gallons (7,571 liters) of me per day through its chambers. No, you don't have much of me in your body, but it pumps me over and over again. Your heart already receives oxygen in the same way as your brain, your foot and the rest of your body: through an artery. Now, even if the h...