Figure 2. Multi-tissue, isometric contractility thought experiments.

A) Isometric arrangement with tissues A–E in series. B) The hydrodynamic pressure chamber equivalent of A, where all chambers communicate through fluid filled channels. Tissues are rigidly attached below, but attached to a moveable piston at the top. C) The tissues are isometrically arranged in a circle, in analogy with A. Pulleys are between tissues, and the pulleys are supported by rigid bars. D) A schematic of the human uterus in cross section. Intrauterine pressure replaces the pulleys and rigid bars of C, and the hydrodynamics correspond with B. In both B and D, each tissue senses the same pressure.