“A pictorial account of the human embryological heart between 3.5 and 8 weeks of development” provides a comprehensive set of 3D-reconstructions of the forming human heart. This seminal paper visualizes cardiac development from the linear heart tube to the four-chamber septated heart and provides a wealth of morphometric data. The reconstructions are all prepared on digital images of sections of human embryos that were staged and processed from the Carnegie collection. The manuscript not only describes the complex 3D changes in words and illustrations, but also provides high resolution interactive 3D-PDFs of each stage, freely available in the supplemental data. The rather complex morphological description of the developmental changes in the heart is brought to life with these 3D-PDFs (using two screens or two computers), helping the reader to obtain a comprehensive insight into the changing morphology of the developing heart. After the reader has digested the wealth of information and details provided, the interactive 3D-PDFs are an excellent source for cardiologists, clinicians, researchers, anatomists, pathologists, teachers and students to teach, study and discuss cardiac development.
The publication provides full cardiac reconstructions of 12 hearts, in which a total of 70 structures have been indicated in concordance with their appearance during development. The structures are traced on high resolution digital images of the sections and are identified/discriminated based on expert knowledge gathered over decades of studying, analyzing and evaluating many hundreds histologically, immunohistochemically and hybridochemically processed human embryos by the senior experts of this publication. Moreover, these 12 hearts are positioned in time such that they describe cardiac development almost as a continuum, i.e. major gaps do not appear, and are compared to mouse and chicken data. Although all morphological changes seem to follow each other fluently in time, one needs to take into account that small differences with other, additional or novel human embryos might be within the normal spectrum due to small variations in the initiation and completion of developmental process (McBride et al. 1971), and are not variants or congenital abnormalities, as such. Moreover, the fact that the entire heart is reconstructed at each stage also allows the reader to compare developmental processes in relation to each other, rather than the conventional description of the development of each individual cardiac component as a separate individual process. Evaluating the series of reconstructions, one realizes that completion of septation is not the sum of different processes, but is rather a contiguous process that starts at the periphery of both poles, develops towards the center and is completed with the septation of the ventricular foramen. A notion that might not have been appreciated in the past.
As in all studies on morphological and anatomical aspects of development, semantic discussion regarding nomenclature and exact borders between different structures among the anatomists, pathologists and researchers will remain, but due to the fact that all primary data and 3D-reconstructions are freely available, such discussions will become more focused.
Our mission: To reduce the burden of cardiovascular disease.