Cardiac nuclei and coronary vessels have the same orientation throughout the left ventricular wall. Mean projection angle for the vessels (red line) and mean orientation of cardiomyocyte nuclei (blue line) as a function of depth into the posterior left ventricular wall for (a) ED9 and (b) ED13, with standard uncertainty u as error bars. ρ is the Pearson’s correlation coefficient. (c) Pearson’s correlation coefficient between the mean vessel angle and the mean cardiomyocyte angle as a function of depth for all n = 4 ED9 hearts and all n = 4 ED13 hearts. Red data points indicate the hearts represented in (a) and (b). ρ = 1 is a perfect linear correlation. (d) Confocal microscopy image acquired at 20 × magnification in an ED13 heart with DAPI (blue) and DiI (red) signal. The DAPI signal was acquired at depth z = 496 μm, and the DiI signal was averaged over the range z = 482 μm to z = 511 μm. Image processed in FIJI.