The changing morphology of the ventricular walls of mouse and human with increasing gestation

FIGURE 1. Workflow of myocardial volume quantifications. Approximately 10 equidistant images were chosen (left image) for labelling of trabecular (trab) and compact (com) myocardium of the left ventricle (LV) and right ventricle (RV). LA, left atrium; RA, right atrium.

FIGURE 2. Change in trabecular volume and proportion in mouse heart development. Notice the strong positive and significant correlations between the volumes of compact and trabecular myocardium (N = 50; N = 5 per day). This demonstrates that compaction, if measurable as a drop in trabecular volume and reciprocal increase in compact volume, does not drive the growth of the compact wall. The line 50:50 indicates the relation at which trabecular and compact myocardium have the same proportion.

FIGURE 3. Gestational changes in the volumes of the ventricular cavities in mice. (a) Short‐axis mid‐ventricular section of the E18.5 mouse ventricle, showing the labelling of central cavity and intertrabecular recesses. (b) Lines Dia and Sys refer to the ratio derived from dividing the adult human normal value of both sexes of left ventricular end‐diastolic volume (Dia) and end‐systolic volume (Sys) by the left ventricular mass (adapted from values from [Luu et al., 2022]; The values are much the same in children [van der Ven et al., 2020]). In the mouse fetuses, the ratio of cavities to ventricular myocardial volume is well below the Sys line, suggesting these ventricles are much contracted. (c) Gestational increase of the volume of the intertrabecular recesses and central cavity of both the left (red) and right ventricle (blue). There is a pronounced decrease in the proportion that the intertrabecular recesses comprise out of the total ventricular cavity.

FIGURE 4. Embryonic development of the ventricular walls of the mouse heart from Embryonic day (E) 10.5 through 13.5. Each row shows the orthogonal sections of the chosen dataset. The left‐hand column shows the short axis plane at more or less the middle part of the ventricle. The middle columns show the so‐called ‘four chamber’ views, which are essentially coronal cuts through the cavity of the left ventricle. The right‐hand columns then show the cut across the long axis of the left ventricle. LV, left ventricle; RV, right ventricle; VS, ventricular septum.

FIGURE 5. Fetal development of the ventricular walls of mouse. The images show the changes occurring from embryonic (E) day 14.5 through day 17.5. As for Figure 4, the columns show the orthogonal views through the ventricle. The panel with the 4‐chamber view from the E17.5 period also contains the equivalent view of the heart of the E10.5 period, shown on the same absolute scale. LV, left ventricle; RV, right ventricle.

FIGURE 6. Perinatal development of the ventricular walls of mouse. The images, with the columns showing the orthogonal sections through the ventricle as used also for Figures 4 and 5, compare the changes from embryonic (E) day 18.5, shown in the upper row, which is the end of gestation in the mouse, to the third postnatal (P3) day, shown in the bottom row. LV, left ventricle; RV, right ventricle.

FIGURE 7. Extensive trabeculation in the adult mouse ventricles. The images show the free wall of the adult mouse ventricles, reconstructed from micro‐CT datasets. While the ventricular base is considered the least trabeculated part of the ventricle, it nonetheless contains extensive trabeculation (see the area around the star). apm, anterior papillary muscle; LA, left atrium; ppm, posterior papillary muscle; PT, pulmonary trunk; RAVJ, right atrioventricular junction.

FIGURE 8. Embryonic and early fetal development of the ventricular walls of human. The bottom row shows the ‘four chamber’ views on the same scale from which it is apparent that the trabecular layer is greater for each stage. LV, left ventricle; OFT, outflow tract; RV, right ventricle.