Figure 1.

Diagram of mouse cardiovascular development. (A) Cardiac crescent formation containing first heart field (FHF) and second heart field (SHF) cells. (B) Cardiac crescent cells migrate toward the midline creating the linear heart tube with its arterial and venous poles and a primitive ventricle. (C) At E8.5, dextral looping of the heart tube leads to formation of the primitive atrial and ventricular chambers in the morphologically correct position. (D) At E9.5, the endocardial cushion cells pinch inward, creating the atrioventricular canal. At E9.5, the endocardial cushions form at the dorsal and ventral lumen of the atrial canal as the endocardial cells undergo epithelial to mesenchymal transition. Cardiac trabeculation initiates at E10.5, creating bundles of cardiomyocytes that extend into the primitive cardiac chambers. Septation initiates at E10.5, starting division of the chambers into the four-chamber anatomy. (E) At E10.5, the outflow tract (OFT) is remodeled leading to the primitive connection of the aorta and pulmonary artery from the primitive ventricle. (F) By E13.5, the heart is fully developed into four distinct chambers with appropriate aorta and pulmonary artery connections to the morphological left and right ventricles (RVs), respectively. Dark pink, FHF; light pink, SHF; light green, atrioventricular (AV) canal; dark blue, endocardial (EC) cushions; yellow green, septation; purple, trabeculations; yellow, OFT.