Fig. 6.

Residual stresses in the myocardium as revealed by microsurgical cuts. (a) Linear cut in heart tube cultured for 24 h. Opening of the circumferential cut indicates tensile longitudinal stress. Cut aspect ratio (α), defined as opening width (w) divided by cut length (l) in the local myocardial plane (see panel (c)), characterizes tension in the myocardium. (b) Aspect ratios for cuts made near the OC or IC of control hearts before (0 h) or after (24 h) culture. Subscripts z and θ denote longitudinal and circumferential tensions, respectively (${\hspace{0.17em}}^{*}p\hspace{1em}<\hspace{1em}0.001,{\hspace{0.17em}}^{**}p\hspace{1em}=\hspace{1em}0.011$). (c) Opening (dashed ellipses) and closure (dashed lines) of representative cuts show residual stress states in control hearts before (0 h) and after (24 h) culture. Outward and inward arrows indicate tension and compression, respectively. Since cuts made near the IC of bent hearts usually do not open, aspect ratios were reported as 0 in (b). Scale bars: 200 μm.