Analysis of the effects of pH and tensile deformation on the small-deformation modulus of calf skin.

A dynamic technique was used to measure the elastic modulus of the reticular dermis of calf skin at a small (0.1%), non-perturbing oscillating deformation. The elastic modulus increases by over an order of magnitude when the tissue is stretched by only 10% before the measurement is made. The results are interpreted by a stochastic model of fiber orientation that includes the orientation of fibers and their straightening out from slack configurations into the load-bearing structure. An equation is derived that accurately describes the course of the modulus-extension curve over a range of pH from 3 to 11, and allows the calculations of the properties and configurations of the slack fibers. One of these is the Young's modulus of a fiber, which agrees well with the previous determinations in neutral medium.