Fig. 9: Changes in the course of the (sub-)aortic and (sub-)pulmonary channels.

The graph (a) shows the changes in the degree of spiraling of the bloodstreams in time and place. The reference plane is sagittal and each dot represents a single embryo. Axial changes in the position of the components of the outflow tract were measured as described in Supplemental Fig. 18. The line connecting the center of the ridges at their proximal ends is shown in purple solid triangular symbols, with the comparable line at their distal ends shown in red open triangular symbols. The blue solid circular and black open circular symbols identify the line connecting the centers of the orifices of the ascending aorta and pulmonary trunk at their proximal and distal ends, respectively, with the distal end of the ascending aorta measured at the pericardial reflection. The brown square symbols show the movement of the distal endocardial ridges relative to the distal orifices of the subaortic and subpulmonary channels. The green diamond-shaped symbols show the asymmetric development of the horns of the aortic trunk measured as the angle of the lines connecting their junctions with the pharyngeal arch arteries. Comparison of the red (open triangular) and purple (solid triangular) symbols shows that, by CS17, the endocardial ridges have lost the initial spiraling arrangement identifiable at CS14. The change in orientation of the myocardialized proximal ridges between CS20 and CS23, as they transform into the subpulmonary infundibulum, accounts for the decline in the purple symbols (see Fig. 10 for morphological details). The compensatory spiraling of the intrapericardial course of the arterial trunks, as shown by the blue symbols, reflects the oblique ventral extension of the aortopulmonary septum, with the black symbols showing that the change in position of the arterial trunks at their connection with the pharyngeal arch arteries contributes to a much lesser extent. The images in panel b (same viewing angle as Fig. 7h–n) are aligned on the location of the developing aortic valve (black line). The horizontal yellow arrow shows the changing position of the (sub-)aortic and (sub-)pulmonary channels in the middle and distal portions of the outflow tract. These channels separate between CS14 and CS15 in the distal outflow tract, during CS16 and CS17 in the middle outflow tract, and between CS18 and CS20 in the proximal outflow tract. All images are also available as preset views in the corresponding 3D-PDFs.