Revisiting the anatomy of the right ventricle in the light of knowledge of its development

Controversies continue regarding several aspects of the anatomy of the morphologically right ventricle. There is disagreement as to whether the ventricle should be assessed in bipartite or tripartite fashion, and the number of leaflets to be found in the tricuspid valve. In particular, there is no agreement as to whether a muscular outlet septum is present in the normally constructed heart, nor how many septal components are to be found during normal development. Resolving these issues is of potential significance to those investigating and treating children with congenitally malformed hearts. With all these issues in mind, we have revisited our own experience in investigating the development and morphology of the normal right ventricle. To assess development, we have examined a large number of datasets, prepared by both standard and episcopic microscopy, from human and murine embryos. In terms of gross anatomy, we have compared dissections of normal autopsied hearts with virtual dissections of datasets prepared using computed tomography. Our developmental and postnatal studies, taken together, confirm that the ventricle is best assessed in tripartite fashion, with the three parts representing its inlet, apical trabecular, and outlet components. The ventricular septum, however, has only muscular and membranous components. The muscular part incorporates a small component derived from the muscularised fused proximal outflow cushions, but this part cannot be distinguished from the much larger part that is incorporated within the free-standing muscular infundibular sleeve. We confirm that the tricuspid valve itself has three components, which are located inferiorly, septally, and antero-superiorly. Shows a dissection of the outflow tract of the right ventricle in which the free-standing infundibular sleeve has been cut back to show the extracavitary tissues that interpose between the cavity of the right ventricle and the sinuses of the aortic root. The right coronary aortic sinus has also been removed. The green "Y" shows the body and limbs of the septomarginal trabeculation. The dissection using a different heart, shows how the pulmonary root can be removed from the base of the right ventricle, exposing the free-standing infundibular sleeve. The base of the ventricular mass is photographed from the atrial aspect. The white arrow with black borders shows the first septal perforating branch of the anterior interventricular artery.image