Spatial situation of the myocardial conal walls.

(A) Right sagittal view of the cephalic portion of a stage 22HH chicken embryo showing the different regions that make up the heart and the location of the conal walls in the organ in situ. Arrowheads: yellow = dorsal wall; green = ventral wall; red = right wall; blue = left wall. (B) Cross-section of the middle zone of the conus at stage 22HH, haematoxylin-eosin stain. Digitally, colours were impressed to the conal walls myocardium as described in section A. Observe a black label immersed in the myocardium of the ventral conal wall. Abbreviations: As = atrial segment; C = conus; Ca = caudal; Ce = cephalic; D = dorsal; L = left; R = right; T = truncus; V = ventral; Vs = ventricular segment.