Bone Marrow Protects Blood Making

Researchers at Harvard have shown that we make blood cells inside our bones because bone marrow sits in one of the safest places in the body from ultraviolet radiation. In early vertebrates, blood-forming tissue originally developed closer to the surface, where UV light could damage the cells that make blood. Over evolutionary time, these tissues moved into the protective interior of bones, where the skeleton shields blood stem cells from harmful UV exposure.

Previous Fact Next Fact