… [H]ealthy bone is disciplined bone, with a structure enviably organized at every scale yet probed, from the caliper calibrations of femurs and phalanges down to the nano dimensions of bone’s constituent atoms. “It’s all in the architecture,” said Robert O. Ritchie, a professor of materials science at the University of California, Berkeley, who studies bone.
Bone is built of two basic components: flexible fibers of collagen and brittle chains of the calcium-rich mineral hydroxyapatite. But those relatively simple ingredients, the springy and the salty, are woven together into such a complex cat’s cradle of interdigitating layers that the result is an engineering masterpiece of tensile, compressive and elastic strength. “We only wish we could mimic it,” Dr. Ritchie said.
Behind the dissolution of bone with age is a system designed for the itinerant years of youth. The skeleton is a multipurpose organ, offering a ready source of calcium for an array of biochemical tasks, and housing the marrow where blood cells are born. Yet above all the skeleton allows us to locomote, which means it gets banged up and kicked around. Paradoxically, it copes with the abuse and resists breaking apart in a major way by microcracking constantly. “Bone microcracks, that’s what it does,” Dr. Ritchie said. “That’s how stresses are relieved.”
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Image courtesy: Prof. Ritchie’s home page.