FIGURE 6. Thermodynamic processes in a pressure-volume loop of a voiding.
During the filling (F), an amount of potential energy represented by the area under the trajectory along the volume change is stored, i.e., the output work is negative (-; red). (B) In the isovolumic contraction (IVC), the bladder performs no mechanical work, i.e., the output work is zero (0). (C) In the emission (E), the bladder performs a mechanical work characterized by the integration of the trajectory along this stage to repulse fluid, i.e., the output work is positive (+; green). (D) In the isovolumic relaxation (IVR), the bladder gains no mechanical work, i.e., the work output is zero (0). (E) The net work done in the entire cyclic process is given by the area enclosed by the loop trajectory of a voiding cycle (net; green).