Amber Dance in Smithsonian:
Bones: They hold us upright, protect our innards, allow us to move our limbs and generally keep us from collapsing into a fleshy puddle on the floor. When we’re young, they grow with us and easily heal from playground fractures. When we’re old, they tend to weaken, and may break after a fall or even require mechanical replacement. If that structural role was all that bones did for us, it would be plenty.
But it’s not. Our bones also provide a handy storage site for calcium and phosphorus, minerals essential for nerves and cells to work properly. And each day their spongy interior, the marrow, churns out hundreds of billions of blood cells — which carry oxygen, fight infections and clot the blood in wounds — as well as other cells that make up cartilage and fat. Even that’s not all they do. Over the past couple of decades, scientists have discovered that bones are participants in complex chemical conversations with other parts of the body, including the kidneys and the brain; fat and muscle tissue; and even the microbes in our bellies.
It’s as if you suddenly found out that the studs and rafters in your house were communicating with your toaster.