atrioventricular canal cushions

a·tri·o·ven·tric·u·lar ca·nal cush·ions

a pair of mounds of embryonic connective tissue covered by endothelium, bulging into the embryonic atrioventricular canal; one located dorsally and one ventrally; they grow together and fuse with each other and with the lower edge of the septum primum, dividing the originally single canal into right and left atrioventricular orifices.
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