I begin my journey into the bone marrow. Have you ever seen how flexible bone marrow is!?! It's really exciting. I form from the hemocytoblast which takes about 2 days. The body produces approximately two million red blood cells per second. So there's a lot of me out there. Finally I can leave and make my way through the capillaries of the veins together with my plasma friend. We take up most of the room because there's so much to go around, but as far as I'm concerned those guys aren't that big to begin with. Finally I move on to what I like to call the big brother of the veins, the capillaries, the arteries. Those are much bigger but they do more work and are stronger, the capillaries are nowhere near as strong! I finally make 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 a day through its chambers, no, you don't have much of me in your body but it pumps me over and over. Your heart already receives oxygenated oxygen in the same way as your brain, your foot and the rest of your body: through an artery. Now, although the h...