Fig. 2: Observation of qualitative morphometric aspects of heart tube morphogenesis.

a, Ventral, dorsal and lateral views of five specimens that are subjectively ordered according to developmental time. Splanchnic mesoderm is represented in blue, and differentiated myocardium is represented in red. The dorsal view shows the progressive dorsal closure of the heart tube and the medial expansion of the SHF. b, Limits of the myocardial differentiated domain depicted on the edges of the myocardium midsurface. The green line represents the boundary between the juxta-cardiac field and the myocardium. The blue line represents the boundary between the myocardium and the SHF. c, Morphology of the myocardium together with the foregut endoderm and the circulatory system lumen. The different lengths of the aortae seen in the three older specimens are due to variable imaging depth. d, Gradual development of the circulatory system in parallel to the foregut endoderm invagination. The ventral view shows the progressive formation of the endocardial lumen, and the lateral view shows the progressive formation of the aortic lumen along the dorsal surface of the foregut endoderm. Abbreviations: JCF, juxta-cardiac field; FGE, foregut endoderm; AP, arterial pole; VP, venous pole; EL, endocardial lumen; AOL, aortic lumen; LSH, left sinus horn; RSH, right sinus horn.