Why do red blood cells get replaced so often?

Red blood cells are being transported all over the body, some having to pass through capillaries as wide as they are. read more

The life of a normal red cell is about 100-120 days. After that the aged red cells are cleared in the spleen. Red cells are constantly being made in the bone marrow to replace the old ones. Red cells lack a nucleus so they don't have the machinery all other cells do to maintain homeostasis. read more

Replacement of our cells also occurs in most of the other tissues in our body, though the cells in the lenses of our eyes and most neurons of our central nervous system are thought to be special counterexamples. read more