A finite deformation theory of the urinary bladder.

In the previous work, A Finite Deformation Theory of Intravesical Pressure and Mural Stress of the Urinary Bladder, we adopted the functional form of the strain-energy density W proposed by Valanis and Landel. In the present paper, the density W of the bladder is expressed as a function of the three principal invariants of the strain tensors. The reason why we adopted these variables is that in the molecular theory of rubber elasticity the W is known to be a simple function of those invariants, and we regarded the urinary bladder as an incompressible isotropic material like a rubber. The result is, however, the same as the previous one. It is also pointed out that the famous Moony-Rivlin plot is not applicable to the bladder.