Red Blood Cells
Red blood cells (or erythrocytes) are the major cellular component of the blood that transport oxygen to other areas of the body. Red blood cells, like all blood cells, are produced in the bone marrow. The average life span of a single red blood cell is 120 days.
Red blood cells contain the protein hemoglobin, which contains iron as a coenzyme, and enables the blood cells to reversibly bind oxygen in the bloodstream. Mammalian red blood cells lack a nucleus and, thus, contain no genetic material of their own. They also lack the machinery for protein synthesis. The lifespan of a red blood cell is about 90 days. Dead and dying RBCs are broken down and disposed of in the spleen and the liver where the released iron is conserved for reuse in the synthesis of new red blood cells.