The oesophageal zero-stress state and mucosal folding from a GIOME perspective

Figure 2 Circumferential experimental and curvefitted stress-strain curves for the muscle (A) and mucosal (B) layers. The curves were fitted by using the Ogden 2nd order strain energy function. The stress-strain curve of the epithelial layer was tested from the mucosal-submucosal layer while the stress strain curve of the MMS layer was assumed to have a similar pattern as the epithelial layer with the magnitude about one order softer than the epithelial layer. For the circumferential uni-axial test and the circumferential planar test the separated muscle and mucosal-submucosal rings were fixed in two L shape rods, one end of the L shape rod was connected to a cannula. The cannulas were connected to rods that could be moved at controlled velocities by a motor. One of the rods was attached to a force transducer. The distance between the rods was adjusted manually to the in vitro length of the strips (reference length). The force (F) was recorded online by a Labview program.