Mean coronary microvasculature orientation in the left ventricular posterior wall. Hearts at two developmental stages (left: ED9, right: ED13) with vessels color-coded based on the local mean helical angle αH, as defined by the coordinate vectors g1–g2–g3. In gray, cross-section views for each heart. Two horizontal cross-sections (g1–g3 plane) at different locations between the apex and the base. One vertical cross-section (g1–g2 plane) intersecting the ventricle from the apex to the middle of the left ventricular base. Volumetric heart surface images (orange) created from the DAPI images with the location of each cross-section indicated (black planes). Two representative hearts shown with n = 4 hearts each for ED9 and ED13. Epi Epicardium, Endo Endocardium. Images rendered in Amira with angles calculated in MATLAB.