Library · Physiology
Life of a red blood cell
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A red blood cell does not last a lifetime: it lives about four months. Since there are so many of them, the body cannot wait for them to run out, and the bone marrow, which is the factory for blood cells, replaces a small fraction of those in circulation every day. It is a fleet on a retirement schedule: new units come in at the same rate the old ones go out.
Retirement happens mostly in the spleen. As it ages, the red blood cell loses its shape and no longer passes easily through the splenic cords, which are narrow passageways. There the cords trap it, and the macrophages of the red pulp, cells that eat whatever needs to be cleared away, are waiting. They eat it and recycle its iron, which is too valuable to throw away.
What is left of the pigment takes another path. The heme group, the part of hemoglobin that carries the iron, becomes bilirubin, the pigment of bile, in a two-step reaction.
In brief
A red blood cell lives about 120 days, and each day the bone marrow replaces roughly 1% of those in circulation.
A fleet on a retirement schedule: new units come in at the same rate the old ones go out.
As it ages it loses its shape, and the splenic cords trap it: macrophages in the red pulp phagocytose it and recycle its iron.
The heme group of its hemoglobin becomes bilirubin, the pigment of bile, in a two-step reaction.
Sources (3)
- National Center for Biotechnology Information, StatPearls PublishingAnemia, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Spleen, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingUnconjugated Hyperbilirubinemia, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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