Continuation of the anatomy and physiology of human blood. The cellular portion of the blood centrifugation was introduced. The red blood cells were shown using micro photographs. Their shape as biconcave discs related to the fact that they do not contain a distinct nucleus and therefore cannot reproduce. Where and how they are produced was discussed, along with a charts of stem cells producing immature and eventually mature red blood cells. Being produced in the marrow of the long bones of the body, like the sternum, led to a discussion of the living nature of bone and blood cells being added to the blood vessels which enter the bone. Study for test on digestion