How does the spleen remove old or damaged RBCs?

The spleen removes old or damaged red blood cells through a mechanical and cellular filtering process that works like quality control for your blood.

Blood enters the spleen and flows into an area called the red pulp, which contains tiny, narrow channels lined with macrophages. Only RBCs that are flexible enough to squeeze through these narrow passages can make it back into the bloodstream. Older or damaged cells, which have lost their flexibility or changed shape, get trapped inside these channels.

Once trapped, splenic macrophages- a type of immune cell—engulf (eat) the old cells in a process called phagocytosis. Inside these macrophages, the red cells are broken down. The hemoglobin from the destroyed cells is split into heme and globin. Iron from the heme is recycled and sent to the bone marrow to help form new RBCs. The remaining parts of heme are turned into bilirubin, which moves to the liver and is excreted through bile.

This process helps maintain a balance: it prevents old, inefficient RBCs from circulating and ensures the body reuses valuable materials like iron. The spleen, therefore, functions as both a filter and a recycling center for your blood—keeping it clean, fresh, and efficient.