Nature Commun. 6, 6649 (2015)

Credit: NATURE PUBLISHING GROUP

Skin is a vital yet often overlooked organ. One of its major functions is to offer the first line of defence against an organism's external environment, with its resistance to tearing being an important characteristic. Although the elastic nature of skin is now well established, its response to loading conditions that would otherwise introduce a tear are less well documented, especially with regard to the underpinning micro-mechanisms. Wen Yang and colleagues now perform a detailed study of deformation in notched rabbit skin specimens, including the use of in situ X-ray diffraction and microscopy, to understand its extraordinary resistance to tearing. It is found that resistance to the propagation of a pre-introduced notch is associated with the curvy and disordered nature of collagen fibrils in the skin, which permits them to straighten, stretch, reorientate and slide in response to an applied load. These mechanisms mitigate further stress build-up at a site of stress concentration, blunting a tear. This demonstration provides another example of how some organisms have adapted to survive in their environment.