Mechanical characterisation of the urinary bladder
The urinary bladder is a central organ of vertebrates. Due to the extreme deformations on the entire bladder tissue and especially the active smooth muscle tissue needs to meet special requirements. Although there are many dysfunctions connected to tissue changes, mechanical analyses are not so common. The development of an electro-chemo-mechanical numerical model based on experimental investigations can be used as a tool for a better understanding of the living system.
To this end, experiments on bladders of domestic pigs are conducted, as their structure and contraction behaviour are similar to those of humans. Using a three-dimensional optical measurement technique a procedure is established to measure the bladder geometry in physiological saline solution. Furthermore, the measurement of the propagation of the action potential during contraction at the bladder’s surface is performed with surface electrode. The different layers of the bladder exhibit different architectures as well as active and passive characteristics that need to be determined. The data is used for an interim validation and a parameter identification of the electro-chemo-mechanical model.
The model developed in the scope of this project can be considered as a compensational method for animal models and, based on the similarity between human and porcine bladders, for human studies. Thus, in future it can contribute to a reduction of animal experiments and can help to have a more comprehensive understanding of bladder functions. Prospective applications of the model could deal with the prediction of different functional impacts of tissue changes (i.e. cicatrisation of the muscle layer due to interstitial cystitis). Therefore, morphological and mechanical changes of the sickened tissue have to be determined experimentally and incorporated into the model.