That anatomy and the same science should still contain such surprises that could change dramatically our knowledge of the human body 

Textbooks showed entrances and exits, but they were enormous arteries and veins at the ends of bones — an impractical route if the body needs a quick burst of the cells forged within our marrow. But in a paper published Monday in Nature Metabolism, a team of German immunologists announced they’d found a whole network of tunnels that explain the escape. While their first observations were in mice, they found a similar map of secret capillaries in humans, too, which may shed light on how certain drugs work.

“These cells seemed to be crossing a wall of solid bone”.

This finding could help to improve drugs prescribed for osteoporosis

That might help explain how immune cells could flood so quickly into the bloodstream — but it also has other implications. The channels in the bone through which these capillaries pass are gouged by osteoclasts, cells that naturally degrade bone so that our skeletons can remake themselves. When the researchers gave mice a common class of drugs often prescribed for osteoporosis, the fact that these drugs stopped osteoclasts in their tracks also meant that they couldn’t form new paths for capillaries. In other words, the drugs might increase bone density but might lessen blood flow between the marrow and the exterior of the bone.

“It’s fantastic,” said Svetlana Komarova, who studies bone biology at McGill University in Montreal, about the potential for better understanding the workings — and side effects — of commonly prescribed drugs (STATS, 01-21-2019).

Photo: 3D imaging inside the bone canal of a mouse.GRÜNEBOOM ET AL./NATURE METABOLISM STATS