Xenbase Image ID: 132243

FIG. 7. Completion of the three-chambered heart (stage 46). Transverse sections are numbered in cranial–caudal sequence, beginning with the most anterior portion of the outflow tract. Blood cells (b) are present throughout the heart chambers and are particularly prominent in the aortic arch (aa), aortic sac (as), and atrial chambers. The spiral valve (sp) can be seen partitioning blood flow from the outflow tract (ot) to the aortic sac. The ventricular myocardium shows extensive trabeculation and local thickening at the atrioventricular aperture (va). The atrioventricular valve (av) separates atrial and ventricular chambers. Dorsal to the ventricle (v), a septum (s) incompletely divides the thin-walled atrial chamber into left (la) and right (ra) atria. In more caudal sections, septation is complete. 3D models reveal the separation of inflow from the sinus venosus (sv) and pulmonary vein (pv), which supply the right and left atria, respectively. At the stage shown, a small connection between the left atrium and the sinus venosus can also be seen (section 40, arrowhead; 3D model, left view). This is lost in older embryos. Image published in: Mohun TJ et al. (2000) Copyright © 2000. Image reproduced with permission of the Publisher, Elsevier B. V. Larger Image Printer Friendly View

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