Fig. 1.

Morphology of foregut and heart tube formation in chick embryo (stages HH5-HH10). (A-E) Brightfield images of embryo (ventral view). Scale bar: 150 μm (for all images). (A′-E′) Schematics illustrating folding of heart fields (HFs). Lateral regions (blue) and medial regions (red) become inflow and outflow regions of the HT (E′). (A″-E″) Schematics of cross-sections indicated by dashed yellow lines in A-E. Red dashed lines indicate HFs in A and anterior intestinal portal (AIP) in B-E. CC, cardiac crescent; CJ, cardiac jelly; FG, foregut; HT, heart tube; iSPL, oSPL, inner, outer splanchnopleure; N, notochord; OV, omphalomesenteric vein. Schematics in A′-E′ are reprinted, with permission, from Kirby (2007); those in A″-E″ are based on drawings by Kirby (2007).