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How are old red blood cells removed and recycled by the spleen and liver?
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blood
Blood sediment in test tubes, showing plasma (clear fluid), red blood cells (red), and the release of hemoglobin into the surrounding plasma (pink).
Red blood cells have an average life span of 120 days. As they age, they become inelastic and are identified and engulfed by macrophagesāspecialized phagocytic cellsālocated primarily in the spleen, liver, and bone marrow.12
Within these cells, the destruction and recycling process occurs as follows:
- Protein and Iron: Hemoglobin is broken down into its component amino acids, which are returned to the plasma for new protein synthesis. The iron is also released into the plasma and transported to the bone marrow to be reused in the production of new hemoglobin; any excess iron is stored within the reticuloendothelial cells for future use.13
- Bilirubin: The porphyrin ring structure of hemoglobin is converted into bilirubin, a yellow pigment. This pigment is transported to the liver, where it undergoes further processing to be secreted into the bile and eventually excreted from the body through the intestine.12
This efficient system ensures that virtually all protein and iron from aging red blood cells are conserved and recycled by the body.1