Figure 12:

Schematic of how fibre uncrimping contributes to tissue mechanical properties. (Top) As a single fibre stretches, it uncrimps, requiring relatively little force until it loses all crimp. The straightened fibre can only be stretched further by making the fibre longer, which requires an increasing force, and so the fibre appears stiffer. A fibre that has uncrimped and is bearing load is called “recruited”. The macroscopic force or stiffness of multiple fibres depends on the distribution of baseline crimp in the fibres. (Bottom row) In a region with fibres of uniform crimp, stretch leads to a macroscopic step increase in stiffness due to the simultaneous straightening of all fibres. In a region with variable crimp, stretch leads to a gradual increase in stiffness due to the progressive straightening of fibres. Fibres with less crimp are straightened and loaded (recruited) before fibres with more crimp. Figure adapted from (Jan et al., 2017a) with permission of the Association for Research in Vision and Ophthalmology.