Natural composites: The structure-function relationships of bone, cartilage, tendon/ligament, and the intervertebral disc

Naturally occurring biocomposites exist in abundance in tissues and organs with great diversity in the animal kingdom. From the incredible toughness of nacre in mollusks to the elegant functional hierarchy of bone, these biocomposites inspire design cues for new biomaterials and novel composite materials. These biocomposites also serve a multitude of functions including those involving mechanical, biological, and biochemical roles that are essential at the cellular, tissue, and organismal levels. Using the multiscale mechanical behaviour of several skeletal tissues (bone, cartilage, tendon/ligament, and the intervertebral disc) as examples of the complex interactive mechanisms that span from the nano-molecular scales up to the macro-tissue scales, we provide an overview of the fundamental building blocks of biocomposites and their eventual roles in physiology. Understanding these features is essential for the recapitulation of function in engineered replacements and regenerative strategies.