Graphic modeling of epithelial transport system: causality of dissipation

The epithelial transport system is a thermodynamic system which is composed of membranes and fluid compartments. The membranes are assumed to be dissipative subsystems in which power dissipates, and fluid compartments are capacitive subsystems in which power is stored. Each subsystem can be subdivided into elementary thermodynamic processes, and can be represented by generalized capacitors, power transducers and resistors in a bond graph. In the modeling of the dissipative subsystem, the causality of the dissipative process was taken into consideration and the representation of power coupling was developed. The dissipative subsystem can be represented by a combination of coupling modules and conductors. Phenomenological equations with parameters from the model were derived. This study shows that the behavior of transport systems can be simulated using these equations.