Red Blood Cell Formation and Destruction

Red blood cells live approximately 120 days and then die and then pieces are recycled. Since red blood cells dispose of their nucleus while a reticulocyte and have no organelles, the RBCs cannot repair themselves or undergo mitosis. This is not inhibitory to their function, however, since their main job is to transport oxygen. Red blood cells are very efficient at this job since they produce ATP anaerobically and thus do not use oxygen in this process. RBC's bind or hold an oxygen molecule to each Iron which is at the center of each porphyrine ring (part of the hemoglobin molecule).

RBC's are phagosized in either the spleen, liver or red bone marrow. The RBC is first most broken down by macrophages into globin and heme. The globin is further broken down into amino acids and are reused for protein synthesis. The iron in the heme is then transported in the blood by a transport protein called transferrin, to the red bone marrow, where it binds to the transferritin and is stored (until used as part of Erythropoiesis). The rest of the heme is converted into biliverdin and then biliruben, enters the blood stream and travels to the liver. It is then secreted into the small intestine as bile. While in the small and large intestines, bile helps to break down large fat molecules. In the large intestine the bilirubin is converted by bacteria into urobilinogen. Some of this is converted into urobilin in the kidney and leaves the body as urine. Most of the urobilinogen is excreted in feces in the form of stercobilin.

I think the most worrisome part of this process for me is that there are some many players or places in this process where things can go awry and cause major problems for the body. And, if the body already has a disease or disorder that effects any of these elements, it becomes an even more compounded problem for the body, bringing it further and further from homeostasis. It seems like there are some naturally built in back-up systems to prepare in a way for such events. For example, if the body is suffering from liver disease and has lost some of its functioning, the macrophages can still phagosize RBCs in the spleen or red bone marrow. The liver however is still engaged in other parts of the process and I am not sure how the body adapts to this malfunction. The disfunction of one part or player in the process produces a domino effect on the rest of process, which, if I understand correctly, continues beyond just this process, effecting possibly many other processes and systems.