Defense Date


Document Type


Degree Name

Master of Science


Mechanical and Nuclear Engineering

First Advisor

Dr. John E. Speich


The bladder wall consists primarily of detrusor smooth muscle. Tension-sensitive nerves in the bladder wall are responsible for providing bladder fullness information that is interpreted as urgency. Bladder wall tension, and therefore nerve output, is a function of bladder volume, shape and material properties. Studies have shown that the bladder wall exhibits acutely regulated detrusor compliance. In addition, bladder shape throughout filling depends on intra-abdominal forces and material properties of the bladder wall, such as regulated detrusor compliance. This thesis focused on modeling the potential influence of acute changes in bladder compliance, shape and bladder wall tension during filling. Laplace’s Law was used to demonstrate how wall tension can vary significantly with geometry in a vessel with uniform internal pressure and constant volume. A finite deformation model of the bladder was previously used to show that wall tension can increase significantly during filling with relatively little pressure change. In this thesis, published experimental data were used to determine ranges for regulated detrusor compliance, and the finite deformation model was expanded to illustrate the potential effects of regulated ix detrusor compliance on filling pressure and wall tension. Also, a geometric model was used to demonstrate that constraining a perfectly spherical bladder to fill as an oblate sphere increases wall tension, and therefore should increase nerve output, for a given volume. In addition, a spheroidal model consisting of three orthogonal circular rings was developed to predict the increase in pressure and wall tension associated with deforming a spherical bladder into an oblate spheroid. Together, these models demonstrate that defects in regulated detrusor compliance and/or acute or chronic changes in bladder shape due to changes in compliance or intra-abdominal forces could contribute to changes in wall tension for a given volume that could lead to urgency.


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